INTERFERENCE AND 
ADAPTABILITY 

AN EXPERIMENTAL STUDY OF THEIR RE- 
LATION WITH SPECIAL REFERENCE TO 
INDIVIDUAL DIFFERENCES 



BY 

ARTHUR JEROME CULLER 



Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of 
Philosophy, in the Faculty of Philosophy, Columbia University 



Reprinted from the Archives of Psychology, No. 24. 



NEW YORK CITY 
JULY, 1912 



INTERFERENCE AND 
ADAPTABILITY 

AN EXPERIMENTAL STUDY OF THEIR RE- 
LATION WITH SPECIAL REFERENCE TO 
INDIVIDUAL DIFFERENCES 



BY 

ARTHUR JEROME CULLER 



Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of 
Philosophy, in the Faculty of Philosophy, Columbia University 



Reprinted from the Archives of Psychology, No. 24. 



NEW YOKE CITY 
JUI/T, 1912 



»«t/<\ 



Press of 

The New era Printing company 

Lancaster, pa 



Gift 

The Univ-M 

oct 3 nn 



CONTENTS 



CHAPTER I 
Introduction 

1. Statement of the Problem 1 

2. Investigations on Interference 4 

CHAPTER II 
The Typewriting and Discrimination Reaction Experiments 

I. Description of the Experiments 10 

(a) Preliminary Group of the Typewriting Experiment 10 

(Z>) Regular Group of the Typewriting Experiment 12 

(c) First Group of the Discrimination Reaction Experiments 13 

(d) Second Group of the Discrimination Reaction Experiments .... 14 

(e) Character Judgments 14 

(/) Subjects 15 

II. Statement of Results 16 

(a) The Typewriting Experiments 16 

(5) Second Group of the Reaction Discrimination Experiments 23 

(c) Character Judgments 24 

(d) First Group of the Reaction Discrimination Experiments 25 

CHAPTER III 
The Card-Sorting Experiment 

I. Description of the Experiment 28 

II. Results of the Experiment 31 

CHAPTER IV 
Individual Differences 

1. Rate of Improvement 51 

2. Initial Efficiency and Plasticity 56 

3. Errors as a Cause of Interference * 59 

4. Variability ri : 66 

CHAPTER V 
Discussion and Summary 

1. Method 68 

2. Relation of Interference to Practise Effect 71 

3. Physiological Considerations 73 

4. Adaptability 75 

5. Ethical Implications 78 

6. Summary 79 



ill 



ACKNOWLEDGMENTS 

The writer wishes to express his deep indebtedness to all of those 
who acted in the capacity of subjects, many of whom sacrificed for 
the sake of the experiment. He is under obligations to Professor 
Bergstrom, whose various articles suggested the use of cards as 
material. For the material in one of the discrimination reaction 
experiments he is indebted to Margaret Hart Strong and Dr. Holling- 
worth. For many suggestions as to methods of treatment and con- 
duct of the experiments, thanks are due to Professor R. L. "Wood- 
worth and Professor E. L. Thorndike. For the suggestion of the 
study, for continual supervision and guidance of the work, the writer 
is most deeply indebted to Professor J. McKeen Cattell. For assist- 
ance in the final arrangement of material the author's thanks are 
due to his wife. 



INTERFERENCE AND ADAPTABILITY 



CHAPTER I 

Introduction 

1. Statement of Problem 

The previous work upon interference of associations has given rise 
to some definite problems. Miinsterberg asked whether a given as- 
sociation can function automatically, while some effect of a previous 
and different association with the same stimulus remains. Also in 
case the new association becomes automatic, what is the condition 
of the former association with the same stimulus ? Does it disappear 
or can the two entirely different movements be connected with the 
same sensation complex, and either of them be called up indepen- 
dently ? x Muller and Schumann worded their problems thus : ' ' When 
a series of nonsense syllables has been learned until the first correct 
repetition is possible, and is then relearned to the same extent after 
a certain interval, will more repetitions be required if in the mean- 
time the syllables of the series have been associated with another set 
of syllables?" 2 Bergstrom devotes his attention to the question 
whether the interference effect is equal to, greater or less than the prac- 
tise effect. 3 Among the purposes of Bair's experiments was "to de- 
termine . . . the increasing amount of interference, first, when there 
is an alteration in the serial order of stimuli, and secondly, when 
there is an alteration of particular responses to particular stimuli 
associated by preceding practises." 4 These investigators have 
asked the following questions. Is there such a thing as true inter- 
ference, and if so how can it be measured? What is the effect of a 
well-fixed association on the formation of a new one with the same 
stimulus, how great is this effect, and can it be overcome? When 

1 Hugo Miinsterberg, ' ' Gedachtnisstudien, Beitrage zur Experimentellen Psy- 
chologies ' 1, 4, 70, 1892. 

2 Miiller and Schumann, i ' Experimentellen Beitrage zur Experimentellen 
Untersuchung des Gedachtniss, Zeitschrift f. Psych, und Phys. der Sinnesorgane, 
6, 173, 1893. 

8 John A. Bergstrom, ' ' The Relation of the Interference to the Practise 
Effect,' ' Am. Jour. Psych., 6, 434, 1894. 

4 J. H. Bair, "The Practise Curve," Columbia Univ. Contributions to 
Philosophy, Psychology, and Education, 5, 9, 5, 1902. 

1 



2 INTEEFEEENCE AND ADAPTABILITY 

the new association has become established what is the condition of 
the former? And finally, can both of them become automatic and 
either be called up without the appearance of the other? 

This paper is concerned with the problem of individual differ- 
ences in interference. It is concerned not primarily with the fact or 
amount of interference when two conflicting associations are op- 
posed, but rather with the rapidity and extent to which the inter- 
ference is overcome by a new association, and with the adaptation of 
the individual to the new association. This of course has special 
interest for the study of individual differences. 

There are two phases of the problem to which the two experi- 
ments will apply. The first is the interference effect of a well-estab- 
lished and long-practised habit association of a series of simple stim- 
uli with equally simple reactions. At the end of the long period of 
practise other reactions are substituted for the same stimuli or series 
of stimuli, and a measure is then obtained of the adaptability of the 
individual to the new association and of the interference effect of the 
previous association upon the new one. The second type is that in 
which two mutually opposing associations are alternated. The inter- 
ference of the one against the other is measured by its resistance to 
the tendency of the opposing one to become automatic. This is 
studied with special reference to individual differences. The first of 
these experiments aims to measure the modifiability of the individ- 
ual, or the building up of a new association against the opposing and 
well-fixed former association. The individual differences will be dif- 
ferences in adaptability to a new situation. The second is the same 
question with which Munsterberg was concerned. The experiment, 
however, is performed under laboratory conditions, with many sub- 
jects, and viewed from the standpoint of individual differences. This 
second phase nicely supplements the first in a study of interference 
and adaptability. The paper will also consider the question of the 
most economical methods of making the two associations automatic. 
In order to determine more specifically what relation the interfer- 
ence effect holds to the practise effect, the results will be considered 
in relation to Bergstrom's contention that the interference effect is 
equal to the practise effect 5 and Munsterberg 's conclusion 6 that the 
two opposing associations can become automatic. 

The question of adaptability is one of great practical importance. 
Yoakum says: "The biologist tells us that the specialist as a mere 
individual must fail in the great life functions. The scientists not 
only demand habits but the power to break those habits. Each and 

5 Bergstrom, loc. cit., p. 441. 

6 Munsterberg, loc. tit., p. 71. 



INTEODUCTION 3 

all abjure over-specialization." 7 Professor MacDougall says: "The 
general character of mental development may be described as adap- 
tation. At all stages and in every phase of its activity the change 
from the earlier to the later form is a reconstruction which tends to 
establish more harmonious relation between the individual and his 
environment. . . . Adaptive reconstruction constitutes the general 
form of change whether the origin of determination be conceived as 
lying in the environment and producing adaptive modification, or 
the element of initiative be considered in the utilization of materials 
for ideal ends. Such adaptation is incessantly renewed so long as 
the individual continues to live. . . . Adaptation involves two fac- 
tors, a form of response already elaborated and an action tending 
to modify the adjustment in conformity with a variation in the 
system of stimuli. The former represents the level of adaptation 
already attained by the organism, the latter represents the incre- 
ment of advance in which the fact of development consists. The 
first of these two factors we call Habit, the second Accommodation. 
Habit constitutes the response of the organism to its environment in 
so far as the system of stimuli possesses permanence in the course of 
experience. Accommodation constitutes the organism's response to 
variations appearing within this system of stimuli. ' ' 8 

Professor MacDougall well describes habit and adaptation in the 
development of the organism. One of my experiments, that on the 
typewriter, aims to fulfil under experimental conditions, his outline 
of habit as a form of response to a system of stimuli already at- 
tained, with a change in the environment such that a new level of 
adaptation is necessary. What I have done in the typewriting ex- 
periment before the break is what he calls habit, the development 
after that break is what he calls accommodation. I am calling it 
adaptation in a more specific sense. 

Adaptation to environmental variations has a very wide signifi- 
cance. Sociologists have long pointed out that the races which can 
most readily change their customs when thrown into new surround- 
ings are the ones which survive. Le Bon says that one of the funda- 
mental differences between the savage and the civilized races is that 
of adaptability. Brinton says the same thing and claims that only 
as there are variations in this respect will the race survive and that 
the most adaptable are the fittest. Bagehot says that the lowest races 

T C. L. Yoakum, ' ' An Experimental Study of Fatigue, ' ' Psy. Rev. Mon. 
Suppl., 46, 116, 1909. 

8 R. MacDougall, ' ' The System of Habits and the System of Ideas, ' ' Psych. 
Bev., 18, 325, Sept., 1911. 



4 INTEBFEBENCE AND ADAPTABILITY 

are enclosed in a cake of custom and the first step of progress is to 
break this preservative habit. 9 

This is also true of smaller groupings of individuals. Giddings 10 
makes a classification of religions on the basis of their tendency to 
break away from hidebound custom. Conversion is a distinct type 
of changed reaction to life and often presents marked interference. 
In every condition of life there are interferences of the old situation 
and adaptability to the new. A strange citizen in a new country, a 
boy from the farm in the city, the freshman in the college, and the 
institutional lad on the streets are all familiar examples. A perfect 
adaptability to all situations is the result of long and varied experi- 
ence. Adaptations are thus a large part of the activity of any ex- 
panding organism. 

2. Investigations on Interference 

The problems of association are among the oldest in psychology, 
both among the philosophers and among those taking a more experi- 
mental attitude toward mental facts. The associationist school at- 
tempted to find the unit of their psychology in the discrete ideas 
and their cohesions, repulsions, and forms of succession. Wundt, 
Ebbinghaus, Muller, Schumann, Galton, and many others of the 
pioneers experimented largely with memory, learning, association 
practise, and other related problems. I shall consider only such in- 
vestigations as bear directly on some phase of the present problem. 

The work that inspired much of later research in interference 
was an investigation of Miinsterberg 's published in 1892. 11 He 
raises the question whether a habit associated with a given sensory 
stimulus can function automatically while some effect of a previous 
and different habit association with the same stimulus remains. 
What is the condition of the old habit when the new one functions 
automatically? Does it disappear or can the two entirely different 
movements be connected with the same sensation complex, and 
either of them be called up independently ? He concluded that both 
can become automatic and need only a slight momentary advantage 
in order to function. The sensori-motor impulse need not pass out 
through both pathways of discharge, like an electrical current in- 

9 See Giddings, "Principles of Sociology"; Brinton, "Basis of the Social 
Mind"; Le Bon, "Psychology of Peoples"; and Bagehot, "Physics and 
Politics." i 

10 F. H. Giddings, "Psychological Classes of Population," Psych. Beview, 
Vol. VIIL, 337, 1901. 

11 Miinsterberg, " Gedachtnisstudien, Beitrage zur Experimentellen Psychol- 
ogie," 1, 4, 70, 1892. 



INTBODUCTION 5 

versely proportional to the resistance, but it can go along either one 
and leave the other undisturbed. Neither is effaced by the repeti- 
tion of the other but both are retained and can quickly function 
automatically. 

For the investigation of this question he pointed out three ex- 
perimental conditions: (a) The movements must be entirely mechan- 
ical so as not to call in the attention; (6) they must be easily varied, 
and (c) they must call in the attention whenever a false movement is 
made or when the reaction is to the previous association. Because 
of the first requirement the experiments could not be performed in 
the laboratory. 

He therefore performed the experiment upon the simple actions 
of his daily life. He had been accustomed to carry his watch in his 
left vest pocket. On the first of the month he put it into his right 
trousers pocket. He noted the number of false movements and be- 
ginnings. On the first of the next month he replaced it in the left 
vest pocket. During the interval he automatically took it out of the 
right trouser's pocket. He then found that to relearn taking it out 
of the left vest pocket took less practise than it previously did to 
learn to take it from the right trouser's pocket. From this fact he 
concluded that some traces of the old habit remained. He found 
that if this alternating process was repeated, the time for each re- 
learning grew less, that both habits constantly grew stronger, and 
that both became automatic. In fact after the third change there 
were no wrong reactions. 

He also made similar experiments with the inkstands on his 
writing table, during one period having the right side bottle and 
during the next the left side bottle filled. He noted the false move- 
ments during each period. His third experiment was the alternating 
use of two doors from his study to the corridor, keeping the one not 
in use locked, and noting again the number of mistakes until each 
became automatic. 

Miiller and Schumann 's 12 problem was whether it will require more 
repetitions to relearn a series of nonsense syllables if in the meantime 
the syllables of the series have been associated with another set of 
syllables. They had two series of twelve syllables, each of which was 
relearned in an average of 7.29 and 7.89 repetitions respectively. 
The second of the series had been united with twelve new syllables 
in the meantime. While relearned almost as quickly, interference 
may have been present, for the second series had been repeated about 
twice as often as the first, and as considerable part of the work of 

12 Miiller and Schumann, loc. cit., 173. 



6 INTEBFEEENCE AND ADAPTABILITY 

learning the series is in learning the individual syllables, the inter- 
ference effect was offset by the greater practise effect. 

Bergstrom made several researches on the relation of interference 
and practise. 13 His first experiment was to study the rate of de- 
crease of interference with the increasing intervals of time between 
the first and second sorting of cards. His subject sorted a pack of 
eighty cards into ten piles, eight in a pile, each card of a given pile 
containing the same picture. In sorting the pack a second time each 
card might be placed in the same position it occupied before or in 
any one of nine other positions. If the former happened there would 
be simple practise, whereas in the latter case the cards enter into as- 
sociations which would exclude the former associations and there 
would be interference effect. The subject first sorted the cards, then 
after a given interval sorted them into ten piles of different posi- 
tions. The intervals used were 3, 15, 30, 60, 120, 240, 480, and 960 sec- 
onds. Bergstrom found that the average difference between the 
3-second and the 8-minute interval was 14.28 seconds, and between 
the one minute and eight minute interval 4.72 seconds, showing that 
about two thirds of the decrease took place in the first minute. In 
twenty-four hours the subject can sort the cards as rapidly as at first. 
Bergstrom did not interpret this as meaning that the neural habit 
of the first association had vanished, but that the second was tem- 
porarily raised above it. The time for the first sorting was about 65 
seconds and for the one immediately afterwards 85 seconds. From 
the false movements which were made he concluded that a strong 
association had been formed. 

The second experiment reported about a year later is more elab- 
orate and contains a fuller discussion of the subject of interference. 1 * 
After quoting the problems of Miinsterberg and Muller and Schu- 
mann he asks what relation the interference effect holds to the prac- 
tise effect. It must either be equal to, or greater or less than, or hold 
a variable relation thereto. He used the same number of cards and 
methods of sorting them as in the previous experiment. The cards 
for the test proper were sorted in the following manner : 

A1A1A2A2 A 8/j 8 

The comparison series was composed of two sets of cards differing 
both from A and from each other, and these, with consequently no 

13 John A. Bergstrom, ' ' Experiments upon Physiological Memory by Means 
of the Interference of Associations," Am. Jour. Psych., 5, 356, 1893. 
"Bergstrom, loc. tit., 433. 



INTBODUCTION 7 

opposing associations, were sorted in like manner eight times. 
Three minutes for each sorting were given, thus allowing forty-eight 
minutes for each test, and giving an interval of nearly two minutes 
between the sortings. 

Bergstrom took eight records for each of the tests, the interfer- 
ence test and the comparison test. For the interference test he used 
either a different set of cards or allowed several weeks to elapse so that 
no practise effect from the previous experiment remained. He had 
one subject and averaged the records for this subject. The compar- 
ison test shows a regular practise curve but the A 1 A 2 series is a hori- 
zontal line. Bergstrom did not interpret this as indicating that the 
interfering associations tended to efface one another. This conclu- 
sion was verified by the fact that a third arrangement of A showed 
the same interference effect as either of the other arrangements. 
He concluded that the interference effect is constant to the practise 
effect and is in fact equivalent to it. 

Bair's experiments were devised to determine the quantitative 
relation between the increasing permanency of an association and 
the succeeding practises, and also the increasing amount of inter- 
ference, first, when there is an alteration in the serial order of stim- 
uli, and second, when there is an alteration of particular responses 
to particular stimuli. He practised a particular order of stimuli 
until they became automatic, then changed the serial order of stimuli, 
or substituted new responses to the old stimuli. The experiments 
were made on a typewriter with several series or colors arranged in 
serial order. A certain key was to be associated with each color, and 
when the color appeared the key was to be struck. The series of 
colors were then changed or a different set of keys associated with 
the colors. 15 

He also sorted cards following Bergstrom 's method but did not 
find nearly as much interference. Taking a lesser number of cards 
he sorted them into six positions. He had them sorted a varying 
number of times and then sorted with an opposing arrangement. 
He found that the difference in time between the last sorting of the 
first arrangement and the first sorting of the second arrangement 
increased with the greater number of practises of the first order. 
He concluded that this greater difference is due to the increased 
speed of the first arrangement and not to interference. 16 

On the typewriting experiment he sums up as follows : ' ' By prac- 
tising a particular reaction or series of reactions to a certain stimulus 

15 J. H. Bair, loc. cit., 5, 14. 

16 J. H. Bair, loc. cit., 34. 



8 INTEBFEBENCE AND ADAPTABILITY 

or series of stimuli, until these responses become automatic, and then 
associating the same response or series of responses with a different 
stimulus or series of stimuli, or a different order of responses to the 
same set of stimuli until the new order becomes automatic, and then 
returning to the first order, going from one order to the other, every 
time the order practised becomes automatic, the time becomes con- 
tinually less for the subsequent adjustments until finally after a 
sufficient number of alternating adjustment practises, either order 
can be responded to automatically, one needing but voluntarily to 
start the response impulse in one direction or the other, and the 
whole series of responses proceed as though that were the only order 
acquired." His results show that both associations become auto- 
matic and that the neural disposition of an old habit does not vanish 
when a new one is formed. He claimed that there is not as much 
interference as Bergstrom finds, and that it is due to indisposition 
rather than inability. 

Mr. W. 0. Beazley's problem was to determine the causes of in- 
terference and to analyze its elements with the purpose of deter- 
mining of what it consists. 17 He paid particular attention to inter- 
ference in relation to motor coordination. In one of his experiments 
the subject was required to strike five keys in a certain order. The 
five keys were of the shape and appearance of piano keys, and were 
constructed in a small box, each key having electrical connections 
with the kymograph. The first and last keys were connected with a 
Hipp chronoscope thus giving the time of the entire reaction. Each 
of the keys had a small picture pasted upon it and the subject had 
before him a paper on which were the same pictures arranged in the 
order in which the keys were to be struck. At the given signal the 
subject struck the keys in the required order, the time was taken by 
the chronoscope and the objective record was made on the kymo- 
graph. Two hundred records were taken, then the arrangement of 
the three middle keys was changed. The first and last were not 
altered as they were connected with the chronoscope. With this 
arrangement two hundred reactions were taken. The second ar- 
rangement was then used with a different order for two hundred 
reactions, and finally the first arrangements was resumed for this 
second order. Four subjects were used. Practically no interference 
was found after the changes. 

The second part of the experiment was similar to the first except 
that the two orders were before the subject, and he was instructed 

17 W. O. Beazley, unpublished research work done at the University of Penn- 
sylvania, 1911-12. 



INTRODUCTION 9 

to react first to the one, then to the other, alternating through the 
entire experiment. Very little interference was found. Mr. Beazley 
concluded that there is no true interference of the old association. 
The only interference is that due to becoming used to the experiment. 
These unpublished conclusions are given only as his tentative 
opinion. 

The other works which will be referred to are not directly on the 
problem but will be used in the discussion, at which time their re- 
sults will be mentioned. 



CHAPTER II 

The Typewriting and Discrimination Reaction Experiments 

The problem as outlined in its broader relations requires a wide 
field of investigation and observation. The changes in reaction 
which a community of foreigners undergo on coming into the new 
conditions of American life, of the American as he goes abroad, or 
of the country lad going into the city furnish interesting observa- 
tion. Mathematical problems in which a new element is introduced, 
a new factor in a problem of logic, a stubborn fact in a theory, a 
shift in economic conditions, all present situations for a broad study 
of adaptability. A study of religious conversion presents a distinct 
type of changed reaction. 1 

The method of the experimental psychologist however is to take 
processes in as simple a form as he can find them. The aim is, under 
laboratory conditions, to exclude all factors except the one which is 
being investigated. Should not the student of individual differences 
do the same thing? The school of Binet and Henri have contended 
that the study of individual differences should be concerned with the 
more intellectual and complex processes because in these the varia- 
tions are more pronounced. 2 Max Brahn in a criticism of their work 
says that the problem of individual psychology can only be investi- 
gated in the simplest forms of psychical activity. 3 To this latter 
principle of method the German and American school has generally 
adhered. 

In all the experiments I have used as simple methods as possible 
in the endeavor to isolate the factor under consideration. Only in 
an auxiliary study of character by the method of average judgment 
is the present study concerned with the more general and intellectual 
differences. This study was made for the purpose of correlation with 
the results of the typewriting experiment. 

(a) Preliminary Group of the Typewriting Experiment 

The first series of experiments were those made on a typewriter 
and will be referred to as the typewriting experiments. There were 

1 See especially E. D. Starbuck, "Psychology of Religion," Chaps. 5 and 13. 

2 Most clearly set forth in ' ' Etude de Psychologie sur les Auteurs dra- 
matique," by A. Binet et J. Passy, Annee Psychologie, I. S. 60-118, 1895. 

8 Max Brahn, "Eeview of the Work of Binet and Passy," Zeitschrift fur 
Psych, und Phys. der Smnesorgane, 12, 280, 1896. 

10 ' 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS U 

two experiments, the preliminary, and the regular. In these two the 
procedure was slightly different. The preliminary experiments were 
made to familiarize the writer with the subject and to suggest meth- 
ods for further work. 

The preliminary experiments were made during the winter of 
1909-10. They were made on an Oliver typewriter, using only the 
middle row of nine keys. A small stand placed beside the machine 
held a cover over the keyboard, high enough so as not to hinder the 
finger or hand movement, yet preventing the subject from seeing 
the keyboard. This cover also held the copy which was to be written 
conveniently before the subject. Each key of the row was assigned 
to a definite finger and was not to be struck by any other finger. 
The fingers of the left hand manipulated the four keys to the left 
and those of the right hand the five keys to the right, the index -finger 
manipulating two keys. The experimenter always required that the 
fingers be in their proper position before the separate repetitions of 
the copy. The thumb was used for spacing. 

For the sake of simplicity numerals instead of letters were 
written. The keys were numbered from 1 to 9 beginning at the left. 
The subject could easily remember the number associated with each 
finger because the numbers came in order from left to right. Each 
number was associated with a particular finger and that finger was 
to strike a particular key. The work of the subject was to make the 
reaction automatic as quickly as possible. 

The following three-place numerals were on the copy before the 
subject and were to be written. 

174 479 853 639 751 628 392 

The objective record was in letters but these were easily checked up 
by a key. 

The subject's hand and fingers were placed ready to write when 
the signal was given. The time was taken with a stop watch. It was 
started on the signal to write and stopped after the last stroke. 
Thirty seconds rest were given between each trial. 

In the preliminary experiment no given number of repetitions 
were given, as was the case in the later experiments. The purpose 
was to practise the series until the subjects had reached their maxi- 
mum speed, and the association had become automatic. This matter 
will be discussed later. 

At this point of practise there was a definite change made in the 
association of the numerals, and this change will be referred to as the 
break. It was simple but definite. Numbers 2 and 3 which had been 



12 INTEEFEBENCE AND ADAPTABILITY 

written by the middle and third fingers of the left hand were here- 
after to be written by the middle and third fingers of the right hand, 
and numbers 7 and 8 were to be transposed to their position on the 
left hand. The number written by the middle finger of one hand 
was to be written by the middle finger of the other and vice versa, 
and the same thing is true of the third finger. The copy was not dis- 
turbed in the least, only the reaction to the numerals mentioned. 
The other associations were not disturbed. The change was made 
to the opposite hand so that the discharge had to follow an entirely 
different channel, and so that there could be no mistake about re- 
lapses, i. e. f reacting to the former associations. Had the change 
been made from one finger to another of the same hand, one could 
not always tell whether a certain error was due to a bungling of the 
fingers or to the former association. After the break the subjects 
again practised until they attained their former efficiency or approxi- 
mated it as closely as possible. 

(b) Regular Group of the Typewriting Experiment 

The procedure in this was the same as in the preliminary experi- 
ment except that it was more rigorous and uniform. The same 
numerals were written under the same conditions up to the break. 
But the number of repetitions was the same for all the subjects 
regardless of the point of efficiency reached. Each subject practised 
the series 130 times. This number of repetitions had been found 
sufficient for the great majority of the subjects in the preliminary 
group. The associations seemed well fixed and automatic by the 
130th trial. It was also found in the preliminary group that the 
only safe measure of the strength of the association was the number 
of repetitions and not the point of efficiency reached. The more 
rapid subjects could soon attain a speed never reached by others. 
But to have introduced the break sooner would have made the 
strength of the associations unequal. 

At the end of the 130th repetition the break was introduced. 
Instead of alternating the fingers writing 2 and 3 with those writing 
8 and 7 as in the preliminary experiment, the fingers writing 1 and 
3 were alternated with 9 and 7 respectively. This change in the asso- 
ciation was explained to them and they were immediately set to writ- 
ing. Other conditions remained the same as before the break. This 
new set of responses was then practised fifty times and the experi- 
ment closed. 

The experiment took six sittings of one half hour or more each. 
Thirty repetitions were given at each sitting. The first four sittings 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS 1?, 

gave 120 repetitions. On the fifth day ten repetitions refreshed the 
habit at which time the break was introduced. Twenty repetitions 
of the new responses were then given on that day and thirty on the 
day following. The experiments were all held in the afternoon or 
early evening and at approximately the same hour each day of the 
experiment. 

Simple errors in writing before the break were counted, grouped, 
and studied for their own interest. But the errors after the break in 
which the old associations persist were separately treated and were 
the direct material for the study of individual differences. These 
will be referred to as relapses and are always to be distinguished 
from errors. 

(c) First Group of the Discrimination Reaction Experiments 

The results reported in this group are only a by-product of the 
experiments on the influence of caffein on the various mental func- 
tions held under the direction of Dr. Hollingworth in the early 
months of 1911. 4 The writer was one of the assistants in those 
experiments and secured permission to use these results for a study 
of individual differences in interference. The data here given are 
those secured during the first week before caffein was used. 

The experiments are those of color discrimination reactions on a 
Forbes chronoscope. The subjects reacted to "red" with the right 
hand and to ' ' blue ' ' with the left. Only reactions of the right hand 
are recorded, while the left set a buzzer going. Mistakes were noted 
as well as double reactions. The data are for 15 subjects, 10 men and 
5 women. There were 140 reactions for each hand taken in fourteen 
sittings of ten reactions each for each hand. At the end of this 
practise period the associations were reversed, blue now being reacted 
to with the right hand and red with the left. The time and errors 
of the right hand were recorded. This association was then prac- 
tised for three periods of ten reactions each. Interference is meas- 
ured by the difference in reaction time of discrimination due to the 
change. The greater frequency of errors after the change is also a 
measure of interference. 

Later on when the subjects had become well practised on the 
Color Naming Test, the Opposites test and the Calculation test, Dr. 
Hollingworth had the correct responses for each of these tests written 
out, and ascertained the time it took the subjects to merely read the 
answers to the tests. The average time was taken as approximately 

4 H. L. Hollingworth, ' l The Influence of Caffein, ' ' Archives of Psy- 
chology, 22, April, 1912. 



14 INTEBFEBENCE AND ADAPTABILITY 

the time required for the perception and pronunciation of the words. 
This average measure of the perception and pronunciation time was 
taken from the average records of the subjects for the test proper. 
This is perhaps as fair a measure of the individual's ability in these 
subjects as can be obtained, for it reduces the time to the "psycho- 
logical limit" if there is such a thing. The results obtained on the 
chronoscope experiments were then correlated with these various 
tests along association lines. 

The chronoscope experiments were conducted by Margaret Hart 
Strong, of the department of psychology of Barnard College, under 
the direction of Dr. Hollingworth. 

(d) Second Group of the Discrimination Reaction Experiments 

This series is similar to the first group except that the reaction 
times for both red and blue were recorded and that only sixty records 
of each were obtained before the color associations were changed. 
After the change thirty reactions with each hand were taken. Before 
the change the right hand reacted to ' ' red ' ' and the left to * ' blue ' ' : 
after the change the reactions were reversed. The group was com- 
posed of twelve men and seven women, all of them subjects in the 
typewriting experiments. The data were secured for the purposes of 
correlation with the results of the typewriting experiments. 

(e) Character Judgments 

This is the only part of the investigation which is not of an 
experimental nature, and which deals with the more general and 
intellectual qualities. Determination of character by the method 
of average judgments is most fully discussed by Professor Nors- 
worthy. 5 This is the method here used. 

An attempt was made to secure competent judgments on the 
following qualities or traits of character: mental balance, intellect, 
emotions, will, quickness, originality, individuality, independence, 
and persistency of habits. Only three of these qualities are discussed 
with reference to our problem, viz., independence, originality, and 
individuality. Sheets were prepared giving the names of the subjects 
in a horizontal column at the top and a vertical column giving the 
qualities in which they were to be rated. These sheets were sent to 
twelve men who were well acquainted with all the subjects to be rated. 
Judgments were secured upon the eight men of the preliminary type- 

6 Naomi Norsworthy, ' ' Judgments of Character, ' ' Volume to William James, 
551, 1908. 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS 15 

writing experiment. Their rating in these qualities was correlated 
with the results of the typewriting experiments. 

The observers were instructed to rate each of the subjects in the 
given traits on the basis of 10. The individual being the most fully 
developed in the trait was to be rated 10 and the lowest conceivable 
was to be rated 1. The most important consideration was to secure 
the same standard of judgment. For this purpose it was felt better 
to make the highest individual conceivable the basis of 10 rather 
than the highest in the group. The writer realizes at the present 
that greater individual differences would have been secured had 10 
and 1 been made the highest and lowest of the group rather than the 
given standards. 

A letter of instruction was given to each of the observers, in 
which the comparative rating of the men was emphasized. Whether 
a man is rated higher or lower is not as significant as whether he is 
in the correct relative position. Only ten judgments were secured, 
as two of the observers did not rate all the men. The judgments for 
a single trait were averaged for each individual and his place in the 
group determined by that average. The method of position in the 
group could not be used because two or three subjects might have 
the same marking, which would introduce too great an error. 

(/) Subjects 

The subjects in the typewriting experiments range in age from 
20 to 35. Only one of them had special training in psychology. 
None of them had had appreciable practise on a typewriter. 

The designations for the different subjects are as follows : 

In the preliminary group : Hf , Co, Sa, Lo, Ja, Se, Hi, St, all 
students of Union Theological Seminary. 

In the regular group : Men, Ha, McC, Br, De, La, CI, students at 
Union Theological Seminary." Ru, clerk in the seminary. 

Women : Mrs. Hf and McC, wives of students in Union Seminary, 
Wh, instructor in psychology in Teachers College. Mo, Gr, Wa, Ta, 
Og, and Ha, students at Teachers College. 

The subjects of the first group of discrimination experiments will 
not be referred to individually. Those of the second group are all 
included in the typewriting groups. In order to facilitate matters 
for the reader all men will be referred to by the designations given 
while the designations of women will be prefixed by Mrs. or Miss. 
The context or definite statement will indicate in what experiment. 
There were twenty-four subjects in the typewriting experiments. 



16 



INTEEFEBENCE AND ADAPTABILITY 



II. Statement of Results 

To make the treatment more coherent a number of questions will 
be discussed in Chap. IV., on " Individual Differences," which will 
embody direct statement of results. Such results as will not be 
needed to make this chapter clear will be given there. 

(a) The Typewriting Experiments 

Table I. gives in condensed form the results of both the prelimi- 
nary and regular groups. The individual records of the 130 repeti- 



TABLE I 

Table I. gives first trial before and after the ' ' Break ' ' in the first two 
columns; the average of the first five likewise in the second two columns; then 
the average of last five. The next two columns give the absolute gain and 
following the percentage of gain before and after "Break. " The last column 
gives the difference between the last five before the " Break' ' and the last five 
after it. A negative sign indicates poorer efficiency after "Break" than before, 
positive better record than before "Break." 









Average of 










Percentage 






First Trial 


First Five 


Last Five 


Absolute Gain 


Of Gain 




O 

I 


z 


.2 


cd 
o 

<D 

pq 


u 

CD 

< 


cd 

M 

O 

cd 
pq 


u 

CD 

< 


0) 

.2 

CD 

cq 


CD 

< 


! 

CD 

eq 


CD 




Ha ... 


36.0 


48.4 


28.8 


29.4 


6.6 


9.8 


22.2 


19.6 


.77 


.66 


-3.2 


Mo ... 


. 75.0 


36.0 


49.0 


26.0 


8.8 


9.6 


40.2 


16.4 


.82 


.63 


— .8 


Ta ... 


54.0 


37.4 


39.4 


29.4 


10.0 


10.2 


29.4 


19.2 


.76 


.61 


— .2 


Hf ... 


35.2 


19.6 


28.8 


20.0 


11.0 


11.0 


27.8 


9.0 


.62 


.45 


.0 


McC .. 


96.0 


39.0 


44.6 


32.6 


10.6 


10.4 


34.0 


22.2 


.75 


.69 


.2 


Wa .. 


69.8 


28.0 


41.4 


26.6 


9.8 


15.0 


31.6 


11.6 


.76 


.45 


-5.2 


Wh . . 


22.4 


27.8 


20.8 


18.4 


6.6 


8.0 


14.2 


10.4 


.69 


.56 


— 1.4 


Og ... 


54.0 


32.2 


34.8 


24.6 


6.8 


12.2 


28.0 


12.4 


.79 


.51 


—5.4 


Gr ... 


57.0 


41.0 


44.6 


29.4 


12.4 


12.2 


32.2 


17.2 


.72 


.58 


.2 


CI ... 


33.2 


24.2 


24.4 


18.8 


6.6 


9.4 


17.8 


9.4 


.73 


.51 


—2.8 


Ru ... 


77.4 


57.0 


47.0 


35.0 


16.8 


13.8 


30.2 


21.2 


.64 


.60 


3.0 


Ha ... 


131.0 


32.6 


58.0 


26.6 


12.8 


14.8 


45.2 


11.8 


.78 


.45 


—2.0 


Br ... 


55.6 


37.0 


41.8 


25.6 


10.6 


14.6 


36.2 


11.0 


.77 


.44 


-4.0 


De ... 


37.0 


33.0 


28.0 


28.0 


9.8 


10.4 


28.2 


17.6 


.65 


.63 


— .6 


La ... 


47.0 


28.0 


33.4 


25.8 


11.2 


13.0 


22.2 


12.8 


.70 


.50 


— 1.8 


McC .. 


71.8 


35.4 


52.4 


31.8 


14.0 


20.0 


38.4 


11.8 


.74 


.38 


-6.0 


Hf ... 


46.2 


31.0 


47.0 


26.8 


17.0 


17.2 


30.0 


9.6 


.64 


.36 


— .2 


Co ... 


51.0 


72.0 


38.6 


42.8 


13.0 


11.6 


25.6 


31.2 


.67 


.73 


1.4 


Sa ... 


49.2 


29.6 


35.8 


21.8 


11.6 


12.0 


24.2 


9.8 


.68 


.46 


— .4 


Lo ... 


60.0 


36.0 


35.0 


30.6 


11.6 


11.2 


23.4 


19.4 


.67 


.63 


.4 


Ja ... 


40.0 


44.0 


32.0 


35.8 


9.4 


11.6 


22.6 


24.2 


.74 


.68 


2.2 


Se ... 


45.8 


31.0 


30.2 


21.6 


10.4 


10.0 


19.8 


11.6 


.65 


.55 


.4 


Hi ... 


41.0 


24.2 


28.4 


17.6 


9.0 


12.4 


19.4 


15.2 


.68 


.31 


-3.4 


St ... 


28.0 


25.0 


23.6 


20.4 


9.6 


9.8 


14.0 


10.6 


.60 


.51 


— .2 



TYPEWRITING AND DISCRIMINATION EXPEEIMENTS 17 

tions are not given as they constitute a simple practise curve, fairly- 
regular and reaching, for most subjects, the physiological limit. The 
table gives the times of the first performance, the average of the first 
five and last five performances, the absolute gain in seconds and the 
percentage of gain. All these are given both before and after the 
break. Plate I. gives the curves for the men and women of the 
regular group. The curves of the preliminary group are not given. 
Both the curves and the table show the practise before the break and 
its effect. The break, it will be recalled, was transferring 1 and 3 
from the fingers of the left hand to the respective fingers of the 
right hand, and vice versa. 

The initial records of the practise curve are very high because the 
subjects were not familiar with the typewriter, and were very awk- 
ward at first. They improved rapidly because of the simplicity of 
the experiment. That the subjects do not rise as high after the break 
as in the initial performance of the practise curve is due to the great 
gain made in learning to use the machine. Four subjects, Co, Ja, 
Misses Ha and Wh, do actually rise higher after the break than at the 
beginning. The curves clearly show that in the fifty repetitions after 
the break the subjects did not attain the level of efficiency before the 
break. An extra column is therefore given in Table I. showing the 
difference between their final performances in the two curves. This 
is obtained by subtracting the average of the last five performances 
after the break from the average of the last five before the break. 
A negative sign indicates that they did not reach their practise level 
by the given number of seconds and a positive sign indicates that 
they surpassed it. By this column we find that among the women 
McC, Hf, and Gr, equalled or surpassed their record before the 
break, while the rest did not equal it. Among the men of the pre- 
liminary group Se, Lo and Co, and among those of the regular 
group, Ru surpassed their previous record, while the rest did not 
equal it. Miss Wa and Mr. McC show the largest difference, they 
being six seconds or more behind their former record. The rate of 
improvement will be dealt with in Chap. IV. 

Perhaps the best index of interference of the old association and 
of its persistency is that of its recurrences. Whenever 1 or 3, and 7 
or 9 were struck with the fingers with which they had been associated, 
the errors were treated as a recurrence of the former association, and 
as such were used as an index of interference. These recurrences 
are called relapses. Table II. shows the distribution of the relapses 
in periods of ten trials and the total number for each subject. 



18 



INTEEFEEENCE AND ADAPTABILITY 




L 



id w ~$ w w &$ m %° & 



Plate I. gives the records of the regular group in the type-writing experi- 
ment. The ordinates give time in seconds and abscissas the number of repetition. 
The curves are made out on the basis of average of five reactions. The individual 
variations are due largely to confusion, errors, etc., and are not important for 



TYPEWBITING AND BISCBIM1NATI0N EXPEBIMENTS 19 



TABLE II 

The distribution of relapses is shown for every ten repetitions after the 
break. Two of the subjects of the preliminary group had more than fifty repeti- 
tions after the break, thus giving a wider distribution of their errors. 

1-10 10-20 20-30 30-40 40-50 50-60 60-70 Total 

6 
15 
11 
12 
66 
59 

2 
54 
56 



16 
20 
39 
33 
15 
18 
42 

12 

12 

24 7 80 

23 

3 

10 

2 11 

16 

With the exception of Hf of the preliminary group who continued 
two periods longer, which accounts for his eightly relapses* the 
women show the greater variability. Mrs. McC has 66 and Miss Wh 
has 2 ; among the men the extremes are De 15, McC 42. Among the 
men of the preliminary group the number of relapses ranges from 3 
for Co to 80 for Hf . Hf however made 31 of those in the repetitions 
beyond fifty which was the total number of repetitions for all of 
subjects except Hf and Sa. With the exception of Hf the distribu- 

our purpose, and to give them would require many charts or cloud the general 
curve. After 130 repetitions the break is shown and the record for the 50 
repetitions after the break with the variations in performance. While some of 
the curves have similar lines they are well enough separated so as not to be 
confused. 



Women 












Ha 


.. 5 








1 


Mo 


.. 12 


1 


1 


1 




Ta 


.. 8 


2 


1 






Hf 


.. 6 


2 


4 






McC .... 


.. 11 


25 


16 


11 


3 


Wa 


.. 16 


2 


13 


16 


12 


Wh 


.. 1 








1 


Og 


.. 39 


3 


6 


3 


3 


Gr 


.. 15 


14 


24 




3 


Men 












CI 


.. 13 




2 


1 




Eu 


.. 15 


2 


3 






Ha 


.. 16 


9 


10 


3 


1 


Br 


.. 8 


12 


5 


3 


5 


De 


.. 5 


7 


2 


1 




La 


.. 2 


4 


2 


3 


7 


McC .... 


.. 3 


2 


14 


10 


13 


Ja 


.. 3 


2 


4 


2 


1 


Se 


.. 7 


1 


4 






Hf 


.. 22 


7 


6 


5 


9 


Hi 


.. 5 


6 


8 


1 


3 


Co 


.. 1 


1 






1 


St 


.. 6 


4 








Sa 


.. 5 


1 


2 




1 


Lo 


.. 10 


4 


1 


1 





20 INTERFERENCE AND ADAPTABILITY 

tion in the preliminary group is very regular, 3, 10, 11, 12, 12, 16 and 
23. Among the men of the regular experiment there are two groups 
one of 1&, 16, 18, and 20, and the other of 33, 39, 42. Among the 
women there are also two groups, the first 2, 6, 11, 12, 15, then a wide 
gap to 54, 56, 59, 66. That this distinct separation into groups 
should exist does not seem to the writer to justify any other state- 
ment than that there is a very wide range of individual differences. 
There is no correlation between the rate of improvement and the 
number of relapses so that those making the greater number of relapses 
did not do so in a sacrifice to speed. The differences in the number 
of relapses are far greater than the differences in rate of improve- 
ment or of speed before the break. 

There were many expressions of difficulty after the break, and 
these were noticeable among the four women making the most 
relapses. One quivered and gritted her teeth, another started to cry, 
the two others claimed they tried hard and one said that it felt so 
funny to start to put one finger down and then stop and put the other 
down. These were the four who made 54, 56, 59 and 66 relapses. 
The number of subjects does not warrant one in concluding that 
there are two types among the women, yet the results do tend to show 
that there is not a single type to which women conform when put 
under such a situation of adaptation to a new element. While the 
men arrange themselves in groups the differences are not so great. 

The men in the preliminary group with the exception of Hf con- 
form closely to a type. Hf, whose time record was poor and who 
thought he had no associations firmly fixed, nevertheless shows an 
abundance of relapses after the break. 

A glance at the table will show interesting differences as to the 
stage at which the relapses occur. The first twenty trials were on the 
day of the break and the other thirty on the day following. With 
most of the subjects the majority of the relapses were made during 
the first ten trials but with some this was not the case. Ha, Mo, Ta, 
and Og, among the women, and CI, Ru, Se, St, Sa, and Lo among the 
men, had a majority of their relapses during the first ten trials and 
thereafter a rapid decrease. But this is not true of Mrs. McC, 
Misses Wa and Gr, nor of Ha, Br, De, McC, Ha, Ja, and Hi among 
the men. They had more relapses during the later periods. Mrs. 
McC made more relapses in each of the following three periods than 
in the first one. McC's relapses rise very decidedly on the second 
day though he had a good record on the first. On the third day Hf 
shows more errors in the first period than on either of the two previ- 
ous days. On the second day he had apparently acquired good con- 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS 21 

trol, but on the third day he had 6, 3, 1, 4, 4, 4, and 2 relapses per 
trial in consecutive trials. Although he thought he had no habit 
formed it proved to have greater and more persistent effect on him 
than on any other individual of the entire group. Miss Gr had 
nearly as many relapses during the first ten trials of the second day 
as on the twenty trials immediately after the break. The compara- 
tive ease with which some of the subjects rose to the situation im- 
mediately after the break, and the relapses to which they were sub- 
ject later on was very noticeable. This is especially true of Hf and 
McC, Misses Wa and Gr, and Mrs. McC. On the other hand Miss 
Og had 39 relapses during the first ten trials, then a very rapid fall- 
ing off. These pronounced differences show that with some the effect 
is more immediate than with the others. The subjects were always 
cautioned on the second day to give their attention to the work so 
as not to make any relapses. In some cases the attention was not so 
well sustained as immediately after the break. Hi who made more 
relapses on the first period of the second day than before admitted 
wavering attention. But as a general rule those who made the most 
errors seemed to try the hardest. This was especially true among 
the women. On the other hand St, who was very rapid and had no 
relapses on the second day had much wavering of attention. De was 
more attentive, less nervous, and had better control after the break 
than before. 

The only three-place number not having a digit affected by the 
break was 628. The 2 and the 8 were however transferred several 
times. The 8 was transferred from the third finger of the right 
hand to the third finger of the left and vice versa with the 2. This 
was done because of the third finger being between the two fingers 
whose associations were transferred. Miss Wa who did this several 
times, said that it seems she must also transpose the other finger 
(pointing to the third finger) because the middle and fourth fingers 
had to change. The same subject also had a number of cases in 
which she struck with the correct finger and then with the other as 
before the break. This seems to be due to a sort of secondary im- 
pulse after the correct finger has responded. There were also a 
number of cases, especially Misses Ta and Mo, where the relapse was 
first made, then the correct association. 

The correlations by the Pearson coefficient between the rate of 
improvement after the break and the relapses are as follows: 

Women r = — .09 P.E. .28 

Kegular Men r=— .76 P.E. .10 

Preliminary Men r = — .69 P.E. .12 



22 INTEBFEBENCE AND ADAPTABILITY 

The correlations between the rate of improvement after the break 
and before are as follows : 

Regular group Men r= .13 P.E. .19 

Women r = .45 P.E. .17 

Preliminary group Men r= — .86 P.E. .06 

These coefficients show a negative correlation between the rate of 
improvement and relapses among the men. Those with more re- 
lapses improve less rapidly and those with fewer relapses improve 
more rapidly. Among the women there is no correlation. This shows 
that speed was not purchased at the price of accuracy nor accuracy 
secured with unlimited time. The two elements of errors and time 
are difficult to adjust so as to secure a reliable measure. With un- 
limited time the subject would have made no relapses, with a given 
speed there would be very many. How can we measure the differ- 
ence when both time and relapses are variable? 

The fact is that in order to secure a measure of the ability of 
breaking the former association the speed could not be set for the 
various subjects, for with some the physiological limit of writing is 
so much lower than with others, that they could at a given speed 
have time to inhibit each tendency to relapse, while the others going 
at their normal speed would have many relapses. The effect of the 
association can be measured only when each subject is writing at his 
best possible speed. Nor can a standard of absolutely no relapses be 
set, for then each single reaction could be fully thought out and the 
new association correctly made. The only true measure is to have 
the subject write at his greatest possible speed and measure both 
time and relapses. 

The negative correlation shows however that speed is not made 
at a sacrifice of accuracy, nor accuracy purchased at the expense of 
speed. This shows that the two elements do not annul each other as 
an index of interference, but rather emphasize the differences. The 
individual differences are greater than either the relapses show or 
than the rates of improvement show and to the extent to which the 
two are negatively correlated is the variability of the group in- 
creased. Again there is no correlation between the rate of improve- 
ment before and after the break except that of .45 P.E. , .17 among 
the women. This shows that the rapidity of improvement after the 
break is not due simply to the general ability to improve, but that 
the differences are entirely due to interference. There is thus no re- 
lation whatever between the performance after the break and before, 
and the individual differences after the break are due to interference. 
The negative correlation between the relapses and the rate of improve- 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS 23 

merit shows that individual differences in adaptability to a new situa- 
tion in the face of the persisting old association are greater than under 
the conditions of ordinary practise. And the negative or negligible 
correlations between the rate of improvement after and before the 
break shows that the differences are not due solely to the same quali- 
ties as make for efficiency in practise. These differences are further 
emphasized by the fact that the variability in the rate of improve- 
ment after the break, as expressed by the Pearson coefficient of varia- 
bility, is 1.6 times as great as that before the break among the 
women, 2.11 times as great among the regular group of men, and 
4.3 as great for the preliminary men. 

(&) Second Group of the Discrimination Reaction Experiments 
These are reported here because they were given directly for 
purposes of correlation with the results of the typewriting experi- 
ment. In this group there were given sixty reactions to each of red 
and blue to the right and left hand respectively. Then the order 
was changed and the colors associated with the opposite hand. The 
results of the twelve men and seven women are given in Table 

TABLE III 
Table III. gives in the first column of each hand the average of the thirty 
reactions previous to the change; in the second column the average of the thirty 
after the change. The third column gives the difference between the two. A 
negative sign indicates that the time was less after the change than before. All 
numbers represent sigmas. 



Miss Wh . . 


Right Hand 

Before After 

Red Blue 

.. 305 333 


Difference 
28 


LeftB 
Before 
Blue 

332 


r and 
After 
Red 

312 


Difference 
—20 


Wa 


.. 345 347 


2 


371 


375 


4 


Ta 


. . 375 387 


12 


392 


380 


— 12 


Gr 


.. 398 376 


—22 


372 


337 


-35 


Mrs. McC . 


. . 443 494 


51 


488 


400 


—88 


Ha 


.. 362 398 


36 


403 


435 


32 


Mo 


.. 431 444 


13 


461 


456 


— 5 


La 


. . 349 303 


— 46 


353 


298 


-55 


McC 


. . 476 478 


2 


477 


476 


— 1 


Br 


. . 391 388 


— 3 


391 


429 


38 


Ha 


... 371 392 


21 


401 


443 


42 


Ru 


. . 276 292 


16 


281 


310 


29 


CI 


... 336 385 


49 


383 


367 


— 16 


De 


. . 316 343 


27 
21 


349 

379 


331 
392 


— 18 


Hf 


. . . 367 388 


13 


Lo 


. . . 226 233 


7 


231 


191 


—40 


St 


. . . 351 353 


2 


332 


343 


11 


Hi 


. . . 308 293 


— 15 


309 


291 


— 18 


Co 


... 283 370 


93 


337 


348 


11 



24 INTEBFEBENCE AND ADAPTABILITY 

III. The results are indefinite because of an insufficient number of 
associations before the change was made. The subjects had not 
reached their practise limit and consequently interference is clouded 
and in some cases the reactions are quicker after the changes than 
before. 

A glance at the table will show that nearly half of the records 
after the change are better than those before. The only explana- 
tion seems to be that the practise limit had not been reached. The 
results are negative and there is no correlation with the typewriting 
experiment. I give the table in order to show all the experiments, 
those which show negative as well as positive results. 

(c) Character Judgments 

Table IV. gives the rating of the eight men in the preliminary 
group of the typewriting experiment in the traits of individuality, 
originality and independence. These figures give the averages of ten 
ratings by friends who lived in the same dormitory with the sub- 
jects and associated with them in the class room. All the observers 
were graduate students. The observers were very conscientious in 
their work and the ratings seem as carefully prepared as any that 
could be secured. With the exception of Se in the trait independence 
no P.E. is over 1, and the median P.E. is .8. This is of course quite 
large considering the small individual differences. The tendency 
among most observers is to mark the individuals high and make very 
little difference between them, giving many of them the same rank. 

TABLE IV 

The average ratings of the character judgments with their probable errors 
are given under the appropriate headings. The fourth column gives the number 
of relapses in the typewriting experiment. The fifth column gives the number of 
mistakes in pronouncing "the" as "a" in a selection of prose of 300 words in 
which the word "the" occurred forty times. The subjects were required to 
read as rapidly as possible and pronounce every ' ' the " as if it were " a. ' ' 





Av. 


Individuality Originality Independence 
P.E. Av. P.E. Av. 


P.E. 


Typewriting 

Relapses 


Reading 

Mistakes 


Se . 


. . 6.0 


1.0 


7.2 


.8 7.0 


2.0 


9 


6 


Lo 


. . 6.0 


1.0 


5.5 


.5 6.0 


1.0 


12 


10 


Hi 


. . 8,5 


.5 


8.0 


.5 9.0 


1.0 


27 


7 


Co 


. . 6.5 


.5 


6.0 


.0 7.5 


.5 


5 


8 


Ja . , 


. . 8.0 


.0 


7.0 


1.0 7.5 


.5 


13 


8 


Hf 


. . 5.5 


.5 


5.0 


1.0 5.8 


.2 


80 


17 


St . 


. . 9.0 


.5 


9.2 


.8 9.0 


1.0 


13 


6 



Sa . . 6.5 .5 6.0 .8 8.0 1.0 11 19 

Av. .. 7.0 1.0 6.6 .6 7.5 .5 22 P.E. 10 10 P.E. 4 



TYPEWRITING AND DISCRIMINATION EXPERIMENTS 25 

The correlations of the rating in these traits with the results of 
the typewriting and reading experiments are given below. Since 
the number of errors and relapses is an inverse index of adaptability, 
the correlation will have an opposite sign from the relation -which 
the two actually sustain to each other. Few mistakes and relapses 
must go with high rating and vice versa in order that there should 
be a positive correlation. The correlations are all negative in sign 
but are therefore given positive to show the real correlation of the 
abilities in breaking the old association. 

Between Individuality and "Eelapses," Pearson Coeff. =.40 P.E. .20 

Between Originality and "Eelapses," Pearson Coeff. =.35 P.E. .21 

Between Independence and "Eelapses, " Pearson Coeff. =.50 P.E. .18 

Between Individuality and Beading Mistakes, Pearson Coeff. = . 66 P.E. .13 

Between Originality and Eeading Mistakes, Pearson Coeff. =.64 P.E. .14 

Between Independence and Eeading Mistakes, Pearson Coeff. = .43 P.E. .19 

Between "Eelapses" and Eeading Mistakes, Pearson Coeff. =.53 P.E. .17 

I was unable to secure competent observers for the subjects in the 
other group, because no sufficient number of observers could be se- 
cured who were acquainted with all the subjects. 

(d) First Group of the Discrimination Reaction Experiments 

Table IX. embodies the results of the first group of the discrimi- 
nation reaction experiments. These results are much more definite 
than those of the second group. The old habit was much better es- 
tablished, there being 140 reactions to red before the change to blue 
was made. In the second group there were only 60. Column D 
gives the interference, i. e., the difference in sigmas between the 
average of the last thirty reactions to red, and the average of the 
thirty to blue after the change. This difference varies among the 
individuals from 2 sigmas to 107. Column F gives the percentage 
of this interference to the subject's practised reaction. Column E 
gives the number of errors due to interference of the old habit> cal- 
culated from the difference between the number of errors in the 
thirty reactions before and after the change. 

The other columns give in seconds the "psychological limit" for 
the tests specified, the time for perception and pronunciation of the 
name being subtracted. There were four women and eight men in 
this experiment. 

The correlation between D and F by the Pearson coefficient is 
.85 P. E., .05. We thus find that the individuals showing the greater 
interference in discrimination time also show greater interference in 
errors. This same thing was found true of the men in the type- 



26 INTEBFEBENCE AND ADAPTABILITY 

writing experiments, while among the women there was no correla- 
tion. 

There is a slight correlation among some of the association tests 
and column D. Between A and D the correlation by the Pearson 
coefficient is .46 P. E., 15, by the method of unlike signs, r = .70. 
There is practically no correlation between D and either B or C. 

TABLE IX 

Table IX. gives the results of the first group of chronoscope discrimination 
experiments obtained under the direction of Dr. Hollingworth. The twelve sub- 
jects are numbered as reported in the caffein experiment. Nos. 3, 6, 11, 15 are 
women, the rest are men. Column D gives the difference in sigmas of the average 
of 30 reactions of the right hand to red, and the average of 30 reactions to blue, 
the subjects being long practised to red and then changed to blue. Column E 
gives the percentage of difference on the basis of their discrimination reaction 
time before the change. Column F is obtained by subtracting the wrong reac- 
tions in 30 trials before the change with the wrong reactions in 30 trials after 
the change, thus giving the greater number of errors under interference. Columns 
A, B, and C, respectively, give the difference in seconds required to take the 
color-naming test (100 colors), the opposites test, and the calculation test, less 
the time of pronouncing the answers to each of the tests when written out. It 
thus gives the time taken for each test, excluding individual differences in 
rapidity of enunciation. The individual records are the average of ten trials for 
each test. 

A B C D E F 



1 


olor-Naming Test 
ifference between 
Naming and Ar- 
ticulation 


(pposite Test Dif- 
ference between 
Associating and 
Naming 


alculation Differ- 
nce between Cal- 
culating and 
Naming 


S.s§ 
£|g 


O « 

. a 
? a 


1 




up' 


u 


O & 








l . .. 


. ... 31.8 


19.3 


63.2 


7 


.022 


1 


3 ... 


. . . . 24.6 


13.4 


59.0 


79, 


.125 


8 


4 ... 


. . . . 14.7 


9.5 


57.4 


32 


.120 


3 


6 ... 


. ... 11.2 


4.2 


30.6 


32 


.100 





7 ... 


. . . . 9.6 


8.9 


32.2 


2 


.006 


1 


8 ... 


. ... 21.5 


20.7 


44.6 


14 


.038 





9 ... 


14.4 


13.1 


45.8 


52 


.164 


4 


10 ... 


. ... 19.7 


19.3 


37.8 


26 


.104 


5 


11 . .. 


23.5 


17.2 


52.7 


38 


.122 


3 


13 ... 


. . . . 34.7 


16.0 


41.7 


107 


.384 


11 


14 ... 


. . . . 20.6 


10.3 


46.0 


35 


.102 


4 


15 ... 


42.5 


28.7 


100.0 


56 


.124 


2 


Av. .. 


. . . . 22.4 


15.0 


50.9 


40 


.118 


3.5 



There does seem to be a clear cut correlation between the perform- 
ance in the color naming test and the interference in the chrono- 
scope discrimination. The naming of colors has an element of inter- 



TYPEWBITING AND DISCBIMINATION EXPEBIMENTS 27 

ference, because the impression of the one color persists during 1 the 
perception and attempted naming- of the second, and the same abil- 
ity that gives efficiency in changing easily from one reaction to 
another would give a high efficiency in naming one hundred colors 
on the color chart. 

The correlation between D and F shows that here as elsewhere 
those having greater interference in time also have greater inter- 
ference in errors and those having less in the one have less in thb 
other. 



CHAPTER III 

The Card-sorting Experiment 

I. Description of the Experiment 

This experiment was made during the winter and spring of 1911 
and the fall and winter of 1912. There were 34 subjects, 17 men 
and 17 women. The experiment took six periods of about 35 minutes 
each for each subject. 

The experiment is an enlargement and modification of the card 
sorting experiment which Bergstrom used. 1 Instead of using cards 
with pictures, which are likely to be of different degrees of complex- 
ity and difficulty, and of different degrees of familiarity with dif- 
ferent subjects, or words, which in themselves might have interfer- 
ing associations, I used "flinch" cards. These are very smooth and 
are easily shuffled, and have simple numbers, and the numbers are 
printed at both ends so that they are always right side up. The 
cards are 2 by 3^ inches in size. The numbers used were from 1 to 
10, and hence are of equal familiarity and difficulty. There were 
eighty cards used, eight of each kind from 1 to 10. 

The cards were not to be sorted at random, as in Bergstrom 's 
experiment, but had to be thrown into boxes made for them. Fig. 
1 shows the boxes and the arrangement for two sortings. These 
boxes made an ideal arrangement for easy sorting. The boxes 
have no bottom so that after each sorting the frame is lifted up, put 
into another position, and is ready for a second sorting. The little 
boxes are four inches square and hence are plenty large enough to 
receive the cards. The back of each box is 2 inches higher than the 
front so that the cards must fall in the right boxes unless wrongly 
thrown. There is no possibility of a card slipping from one section 
to another and a card on the wrong pile means that it was thrown 
wrongly. The subjects were required to pick up cards which they 
dropped and to pick them out of the box if wrongly thrown. Thus 
there are no errors to take into consideration. 

The time was taken with the stop watch. The watch was started 
when the signal was given to the subject and stopped when the last- 
card was thrown. The cards were always thoroughly mixed, special 
care being taken that two of the same kind did not follow each 
other. There were enough packs of cards and enough helpers to 

1 Bergstrom, loc. cit., pp. 434, 435. 

28 



TEE CAJW-SOBTIXG EXPEBTMEXT 



'29 



■ 


9 
r 6 

10 

AT S 


pPWIR JKlIf 


mm " p9 


W P 




BURR 

mum 




Fig. 1. Description in text. 

keep the subject going no matter how rapid he was. A rest of 30 
seconds was always given between sortings whether of the same or 
opposing arrangements. This was kept constant for Bergstrom had 
shown that the interference decreases rapidly with the increase of 
the interval between the sortings. Sixteen sortings were taken at 



30 INTERFERENCE AND ADAPTABILITY 

one sitting' which continued for six days giving a total of 96 sort- 
ings, 48 of each arrangement. The element of fatigue did not enter 
in at all, as at no time were more than sixteen sortings held. 

The subjects were divided into four groups, an equal number of 
men and women in each group. The men and women for each group 
were chosen at random. The first group is composed of four men 
and four women and is known as the "practise group" or Group I. 
This group sorted the cards only into the one arrangement and are 
used to determine the practise curve without interference as a com- 
parison test for the other three groups. They sorted the cards 48 
times. 

The second group was composed of three men and three women. 
They sorted alternately according to the following formula : 



A 1 A 1. A2A2A3A3 A 48 A 



48 



(A 1 throughout the discussion will indicate the first arrange- 
ment, and A 2 the second, while the exponential numbers will give 
the number of times the respective arrangements are sorted.) Each 
arrangement was thus sorted eight times each day for six days, alter- 
nating with the other arrangement. Bergstrom had the alternating 
arrangement, but the conditions here are different from those in 
Bergstrom 's experiments in that the interval between the sortings is 
thirty seconds, while his were nearly two minutes; in that each ar- 
rangement is fixed for all the subjects and kept constant; and in 
that it is continued six times as long. This group will be referred 
to as the alternating group or Group II. 

The third group was under the same conditions as Group II., 
except that the first arrangement was sorted four times, thus being 
fixed more firmly than in Group II., then the other arrangement 
four times, and then to the first again according to the following 
formula : 

44J4/44/J4 /I 48 /j 4S 

On the same day there were only two periods of each arrange- 
ment, which made sixteen sortings in all. The first arrangement for 
the first section was not subject to interference, but the second ar- 
rangement always was and the second section of the first was also. 
This group had seven men and seven women and will be referred 
to as Group III. 

The fourth group was like the third except that the cards were 
sorted into the first arrangement eight times, and then eight times 
into the second according to the following formula : 



AS AS AS AS A 48/1 

JA X , J± 2 , J± x , J± 2 , . . ., Ji. 1 ,J±. 



4 8 



TEE CARD-SORTING EXPERIMENT 31 

In this group the first arrangement was never subject to immedi- 
ate previous interference, as only one turn at each arrangement could 
he had at a sitting. The second arrangement had the interference 
effect of eight previous sortings of the first, but was itself continued 
for eight, giving it greater time to overcome the interference. This 
group, which will be referred to as Group IV., had three men and 
three women. 

The experiments were held in the afternoon or early evening on 
successive days. In several cases a day had to be missed, but no 
influence was detected. Where however the subject had to remain 
away for considerable time, he had to be dropped. Several subjects 
had to be thrown out because of such irregularity. 

The subjects ranged in age from 16 to 36. Only two of them 
had special training in psychology. They will be referred to by the 
following designations. 

Group I. Men : Wa, Co, 01, and Be, all students at Union Theo- 
logical Seminary. Women : Sm and Co, clerks ; Fo and St, students. 

Group II. Men : Em, clerk ; Gr, theological student ; My, gradu- 
ate student in psychology. Women : Cu and "Sit, married women 
with high school training; Bk, musician. 

Group III. Men: Ca, Si and Dr, theological students; Wi and 
Rd, high school students; Sv, architectural draughtsman. Sp, sales- 
man. Women : Ku, Wo, Sv, Su, Ar, wives with high school and col- 
lege training ; Br and Th, clerks with high school training. 

Group IV. Men : As and Bl, theological students ; Cu, graduate 
student in psychology. Women: Mrs, Th, w T ith high school train- 
ing, Mor and Ag, music teachers. 

All men will be referred to by the initials and women will be 
referred to by initials prefixed with Mrs. or Miss. The context or 
definite statement will show in what group the subject under con- 
sideration performed. 

II. Results of the Experiments 

As stated in the description of the experiments Group I. will be 
used as a practise group for comparison and the other three groups 
in a study of interference. Group II. sorted the cards alternately, 
Group III. sorted them four times by one arrangement and then 
four times by the other, and Group IV. sorted them first eight times 
the one way, then eight times the other. 

The individual records of Group III. are given in Table V. This 
group had seven men and seven women and is the only one that will 
be used for a study of individual differences. The other groups had 



32 INTERFERENCE AND ADAPTABILITY 

three men and three women each and have their value principally 
in the discussion of the relative interference effect of the various 
methods, and the rapidity with which the associations can become 
automatic in each. 

The curves for this group are given in Plate II. for the women 
and III. for the men. Plate IV. shows the average curves for the 
men and women of this group, together with the performance in 
the practise group for purposes of comparison. The Roman type 
of the table gives the records of the first arrangement and the Italic 
type those of the second. 

Table VI. gives the averages and their deviations for the four 
groups. Plate V. gives the graphic record of the averages for 
Groups II. and IV. The Roman and Italic types give the records 
of the first and second arrangements respectively. Since the first 
group had only 48 sortings and those of only one arrangement they 
are all printed in Roman numerals and are continued through the 

Plates II. and III. give the curves for the women and men, respectively, in 
the card sorting experiment, Group III., Arrangement A ± four times, A 2 four 
times. Each plate gives seven curves, four in the lower sections and three in the 
upper. The ordinates give the time in seconds and the abscissas the number of 
times sorted. The days are marked by the lines with the numerals, each day 
having sixteen performances, and the change from one arrangement to another 
is shown by the smaller graduated scale. The procedure each day is made clear 
by the arrangement being shown on the third day. The rise in time after each 
change is clearly seen in both, though much more pronounced with the men. The 
curves in the lower sections are allowed to extend into the upper at the beginning 
to show them in full. 

To avoid overcrowding the plate the following references to curves are 
given: Plate II. Women: Lower section, heavy line, Mrs. Wo; heavy dotted, 
Miss Br; light, Ku; light dotted, Sv. Upper section, heavy, Mrs. Ar; light, 
Mrs. Su; light dotted, Miss Th. 

Plate III. Men: Lower section, heavy, Wi; heavy dotted, Sv; light, Sp; 
light dotted, Ed. Upper section, light, Ca; heavy, Dr; light dotted, Si. 

Plate IV. gives the average curves in the card sorting experiment, Group 
III., for the 7 men and 7 women. The average practise curve for the men and 
women is also given. Solid line curve gives records of women, dotted of men. 
The change in arrangement is so clearly seen in the spires of the curves that no 
marking is necessary. Every day has its three rises after the three changes. 
It is also noticeable that each day's beginning is about at practise level of 
previous day. The curves of the men will be seen to rise higher after the change 
than the women, although their average is lower until the fourth day, when they 
begin to remain as low or lower. 

Plate V. gives the curves for men and women in the second and fourth 
groups, Group IV. above, Group II. below. Solid line, women; dotted line, men. 
The scale on the ordinate is just half that of the average curve of Group III. 



TEE CAED-SORTIXG EXPERIMENT 



33 



® co O CV , ^ .}o °0 A <0 00 ■ O 02 

Q) CO OQN^ *Q ^ ^ (ft CO, OQ N- 

i -i I — i^t^l — r — i — i ^-i--- r>j. 






1V0 




§ 0) OQ CO ^ ^ "0 ^5 0) CO 00 N ^) *o ff 



34 



INTEEFEBENCE AND ADAPTABILITY 



£* t VO CO O C\J ^ JO 00 S- to 00 Q CSJ ^ ^0 5 

^ S 0) oo oo ^ vo v> ^ S (n co oo K ^ io * 




* § $ 



CO^VO^^Q^COCO^AO 1 ^^ 



THE CABD-SOBTING EXPEBIMENT 



35 




36 



INTEBFEBENCE AND ADAPTABILITY 



^ vo co o <v ^ jo 5P <^ *o co o w ^ }o 



CO 




tt*s ^il^HUiil 



THE CARD-SORTING EXPERIMENT 37 

TABLE V 

Individual Eecords of Women in Card- sorting, Group III 

The Roman type gives records in seconds of Arrangement 1; Italic type, 

of Arrangement 2. Spaces separate successive days. 

Ku Sv Wo Br Su Th Ar Average A.D. 

1 107 138 86 140 103 118 104 113.7 15.8 

2 106 122 87 109 87 106 92 101.3 10.9 

3 103 122 91 104 82 92 85 97.0 10.9 

4 97 104 79 118 79 92 79 92.6 11.4 

5 132 126 98 ISO 113 121 103 117.6 11.0 

6 119 120 86 105 81 97 87 99 .4 13.1 

7 97 107 75 106 75 91 79 89.7 11.4 

8 96 112 72 100 71 80 76 85.2 13.8 

9 101 120 89 105 104 100 100 102.6 5.9 

10 98 111 85 94 89 84 82 91.6 7.1 

11 97 118 71 93 87 100 76 91.7 11.7 

12 86 109 84 90 85 82 70 86.6 7.1 

13 104 123 88 112 Uh 104 85 104-3 10.3 

14 91 116 80 102 93 89 76 92.4 9.6 

15 101 104 73 93 72 81 73 85.2 12.2 

16 95 128 68 89 72 86 69 86.7 14-4 

17 92 109 79 103 75 92 95 92.1 8.7 

18 80 100 72 87 66 83 76 80.6 8.0 

19 85 101 74 85 68 72 74 80.1 9.0 

20 79 88 70 79 66 73 72 75.3 5.7 

21 102 111 87 96 108 100 94 99.7 6.3 

22 95 97 7// 82 7^ 76 78 82.1 8.0 

23 92 94 76 90 67 75 76 8I.4 9.0 

24 89 102 76 81 71 78 66 8O.4 8.7 

25 100 109 86 100 98 102 100 99.3 4.1 

26 85 109 80 101 75 85 87 88.9 9.2 

27 84 100 73 105 73 74 73 83.1 11.3 

28 80 103 69 91 69 81 67 79.4 9.4 

29 104 118 79 84 91 90 86 93.1 10.1 

30 94 118 71 81 70 73 69 82.1 13.6 

31 94 95 71 88 78 78 76 82.9 8.1 

32 84 99 71 82 67 75 61 77.0 9.7 

33 90 95 76 80 70 73 81 81.0 6.6 

34 78 93 68 80 64 67 75 75.0 7.4 

35 91 86 67 71 61 66 79 74.4 7.4 

36 91 80 68 85 65 68 59 73.7 10.3 

37 105 92 83 91 95 81 80 89.6 7.0 

38 90 93 75 80 76 75 71 80.0 6.7 

39 82 94 71 80 64 75 65 75.9 8.1 

40 84 91 71 77 60 67 60 72.6 9.4 

41 98 108 77 89 97 84 73 89.4 10.0 



38 INTERFERENCE AND ADAPTABILITY 

TABLE V (continued) 

Ku Sv Wo Br Su Th Ar 

42 87 99 76 88 87 77 70 

43 78 100 74 89 83 70 64 

44 73 101 65 90 62 77 61 

45 89 102 72 89 87 76 76 

46 79 90 66 86 72 73 70 

47 84 98 71 79 79 74 66 

48 74 99 78 79 59 74 61 

49 84 83 66 78 75 70 66 

50 78 82 64 84 58 68 58 

51 70 84 64 78 58 71 57 

52 77 92 58 75 55 67 54 

53 90 103 73 89 78 72 86 

54 85 89 73 81 60 77 71 

55 84 95 66 79 57 78 66 

56 77 91 64 77 67 71 65 

57 96 110 76 103 86 79 74 

58 86 95 65 87 76 79 64 

59 90 87 64 86 67 76 55 

60 84 89 65 89 59 81 60 

61 92 108 68 95 79 82 86 

62 84 102 67 71 73 75 84 

63 79 89 70 85 80 7^ 62 

64 85 96 63 77 55 73 64 

65 80 93 63 77 76 69 70 

66 74 88 64 73 64 65 61 

67 78 89 54 70 57 63 64 

68 82 86 59 71 54 65 60 

69 96 92 69 83 77 84 77 

70 93 93 62 75 66 77 64 

71 87 92 62 70 59 79 77 

72 78 89 59 69 53 78 58 

73 84 102 65 82 83 82 81 

74 78 95 62 77 74 67 58 

75 79 90 62 73 65 70 59 

76 75 92 65 75 64 71 58 

77 92 101 69 85 89 76 77 

78 84 90 63 76 79 72 71 

79 85 97 58 69 60 75 65 

80 60 87 57 69 64 77 55 

81 71 85 64 80 64 67 71 

82 76 82 55 72 56 65 62 

83 70 82 57 69 52 62 68 

84 75 84 58 72 49 61 58 

85 88 99 66 7^ 94 73 80 

86 81 96 59 68 76 74 63 

87 81 87 61 67 61 71 61 



Average 


A.D. 


83.4 


7.7 


80.0 


7.9 


75.3 


12.0 


844 


8.4 


76.3 


^■4 


78.7 


7.6 


75.0 


9.0 


74.6 


5.3 


70.3 


7.6 


68.7 


8.0 


68.3 


11.4 


84-4 


8.6 


76.6 


7.3 


75.0 


10.0 


73.1 


7.3 


89.3 


11.7 


78.8 


9.1 


75.0 


11.1 


75.3 


12.0 


87.1 


9.6 


79.3 


9.1 


77.0 


7.1 


73.3 


10.9 


75.4 


8.6 


69.9 


7.3 


67.9 


9.6 


68.1 


10.0 


82.7 


7.1 


76.6 


9.6 


75.4 


9.4 


69.1 


10.9 


82.7 


6.4 


73.0 


9.1 


71.3 


8.0 


71.4 


8.0 


83.4 


8.1 


76.3 


6.9 


73.1 


11.3 


67.0 


9.1 


71.7 


6.3 


66.9 


8.4 


65.1 


7.3 


65.3 


10.0 


82.0 


9.8 


73.7 


9.1 


69.9 


8.4 



TEE CARD-SORTING EXPERIMENT 39 

TABLE V (continued) 

Ku Sv Wo Br Su Th Ar Average A.D. 

674 6.8 

83.7 9.4 

70.7 11.1 



88 ... 


... 73 


81 


60 


70 


57 


69 


61 


89 ... 


... 87 


100 


71 


73 


97 


77 


81 


90 ... 


. .. 77 


100 


58 


74 


57 


74 


58 


91 ... 


... 70 


94 


58 


77 


57 


72 


64 


92 ... 


. .. 74 


92 


57 


71 


54 


71 


56 


93 


... 85 


99 


65 


75 


80 


76 


77 


94 ... 


... 84 


96 


57 


68 


69 


70 


60 


95 ... 


... 74 


92 


57 


73 


54 


70 


59 


96 ... 


... 80 


78 


61 


64 


64 


64 


65 










TABLE V 







67.7 


9.3 


67.9 


10.4 


79.6 


U 


72.0 


10.3 


68.4 


11.4 


68.0 


6.3 



Individual Kecords of Men in Card-sorting, Group III 

The Boman type gives records in seconds of Arrangement 1; Italic type, 
of Arrangement 2. Spaces separate successive days. 





Ca 


Si 


Dr 


Sv 


Wi 


Sp 


Rd 


Average 


A.D. 


1 ... 


... 98 


122 


118 


117 


98 


145 


127 


117.9 


11.7 


2 ... 


... 79 


99 


96 


99 


91 


120 


120 


100.6 


10.9 


3 ... 


... 80 


90 


86 


83 


95 


110 


115 


94.1 


10.7 


4 . .. 


... 75 


89 


89 


74 


88 


99 


109 


. 89.0 


8.6 


5 ... 


... 120 


146 


118 


105 


134 


152 


152 


132.0 


15.4 


6 ... 


... 95 


127 


105 


85 


98 


110 


139 


107.7 


144 


7 ... 


... 82 


111 


96 


75 


86 


129 


109 


98.3 


15.4 


8 ... 


... 7-4 


94 


92 


70 


90 


115 


110 


92.1 


9.6 


9 ... 


... 107 


135 


121 


116 


133 


117 


125 


122.0 


7.7 


10 ... 


... 86 


112 


94 


86 


116 


120 


92 


100.1 


13.0 


11 ... 


... 83 


94 


88 


72 


93 


98 


86 


88.0 


6.0 


12 ... 


... 70 


94 


85 


73 


92 


95 


76 


83.0 


9.0 


13 ... 


... 108 


127 


115 


103 


104 


129 


122 


115.4 


9.0 


14 ... 


... 86 


112 


91 


84 


92 


110 


105 


97.1 


10.1 


15 ... 


... 70 


98 


80 


79 


90 


97 


91 


88.1 


10.1 


16 ... 


... 81 


85 


75 


80 


85 


95 


93 


85.6 


44 


17 ... 


... 84 


97 


83 


86 


75 


102 


100 


89.6 


8.5 


18 ... 


... 71 


84 


78 


78 


76 


91 


85 


80.3 


5.1 


19 ... 


... 66 


77 


73 


72 


76 


88 


80 


76.0 


% 4.6 


20 ... 


... 62 


84 


72 


67 


73 


87 


84 


75.7 


8.1 


21 ... 


... 103 


121 


104 


92 


93 


129 


120 


110.2 


13.6 


22 ... 


... 77 


113 


78 


85 


80 


115 


95 


91.9 


134 


23 ... 


... 71 


85 


76 


80 


81 


107 


82 


81.7 


5.3 


24 ... 


... 64 


70 


72 


71 


79 


92 


77 


75.0 


6.4 


25 ... 


... 90 


96 


107 


80 


110 


121 


102 


100.6 


11.1 


26 ... 


... 70 


75 


87 


70 


90 


96 


90 


81.4 


7.6 


27 ... 


... 63 


88 


76 


79 


84 


92 


80 


80.3 


6.4 


28 ... 


... 63 


69 


69 


70 


100 


82 


74 


75.3 


7.3 


29 ... 


... 81 


101 


104 


94 


93 


107 


106 


98.0 


7.3 


30 ... 


... 71 


76 


78 


86 


81 


100 


80 


80.7 


7.5 


31 ... 


... 60 


67 


73 


79 


80 


87 


75 


74-4 


6.5 


32 ... 


... 63 


86 


72 


69 


83 


103 


82 


79.7 


10.0 



40 INTERFERENCE AND ADAPTABILITY 



TABLE V (continued) 

Ca Si Dr Sv Wi Sp Rd Average A.D. 

33 85 75 72 75 85 88 80 80.0 5.1 

34 71 69 70 67 82 82 69 73.1 5.2 

35 62 82 69 61 69 82 72 71.0 6.4 

36 58 . 64 66 58 76 78 71 67.3 6.4 

37 77 124 92 94 89 118 95 96.7 154 

38 69 83 72 79 78 97 81 794 5.5 

39 62 76 69 66 87 89 75 74-9 7.6 

40 67 76 64 66 83 71 76 71.9 54 

41 86 95 85 92 90 108 87 91.9 6.0 

42 64 94 74 68 86 84 73 77.7 9.0 

43 60 82 70 65 86 85 69 73.9 9.0 

44 55 67 63 59 86 72 65 66.7 7.0 

45 92 103 84 88 73 117 88 92.1 7.2 

46 67 83 82 76 72 92 73 77.9 6.5 

47 61 75 75 65 70 87 68 71.9 6.1 

48 64 68 68 58 91 76 72 71.0 7.1 

49 77 78 68 69 71 87 76 75.1 5.0 

50 58 69 66 52 75 76 68 66.3 6.4 

51 54 65 63 52 67 73 67 63.0 5.5 

52 48 58 64 54 67 74 65 61.4 6.6 

53 87 94 91 81 87 105 85 90.0 5.7 

54 70 83 80 65 70 93 74 76.1 7.7 

55 61 72 67 69 69 80 78 71.1 5.3 

56 61 64 65 63 74 79 67 67.6 5.3 

57 78 90 79 85 91 123 76 88.9 10.7 

58 70 79 73 78 75 93 72 77.1 5.3 

59 66 73 71 59 82 86 68 72.1 7.3 

60 63 73 63 54 80 78 73 68.3 6.4 

61 68 99 78 72 76 99 82 82.0 9.7 

62 68 82 71 61 83 88 73 75.1 7.9 

63 67 71 65 59 70 77 69 68.3 3.9 

64 58 66 61 62 72 81 70 67.1 6.1 

65 77 74 65 65 73 83 72 72.7 4.6 

66 54 67 64 59 66 85 68 66.1 6.1 

67 50 59 65 55 64 79 64 62.3 6.6 

68 48 62 61 50 59 72 62 59.1 5.9 

69 68 90 78 85 74 114 U 84-7 10.0 

70 64 68 65 64 69 90 66 694 6.3 

71 57 74 62 60 65 100 70 69.7 10.0 

72 54 64 63 54 66 92 70 66.1 84 

73 77 97 81 89 83 91 78 85.0 6.3 

74 70 76 73 64 75 85 80 74.7 4.9 

75 57 79 71 63 69 86 69 71.0 5.4 

76 55 72 64 60 65 76 71 67.6 7.4 

77 71 88 78 75 73 100 82 81.3 8.0 

78 60 72 66 64 66 85 66 68.4 5.6 

79 59 73 67 59 66 76 70 67.1 5.0 

80 51 70 67 56 68 88 72 674 8.0 



THE CAED-SOETING EXPEEIMENT 41 



TABLE V (continued) 



Ca Si Dr Sv 

81 54 67 66 58 

82 50 64 62 51 

83 49 58 63 54 

84 44 60 61 52 

85 73 79 76 83 

86 55 87 65 66 

87 51 71 65 56 

88 53 61 59 52 

89 65 84 81 85 

90 57 74 69 64 

91 57 66 66 63 

92 51 67 62 54 

93 81 86 83 77 

94 65 78 67 61 

95 57 64 62 59 

96 57 65 60 53 



Wi 


Sp 


Rd 


Average 


A.D. 


65 


85 


73 


67.0 


7.1 


59 


83 


60 • 


61.1 


7.0 


69 


84 


64 


62.9 


8.1 


64 


78 


63 


60.3 


7.0 


68 


95 


78 


79.3 


5.4 


69 


82 


62 


694 


8.9 


60 


89 


70 


64-6 


7.7 


61 


84 


66 


62.0 


6.9 


72 


108 


83 


82.6 


8.6 


68 


91 


73 


70.9 


7.3 


65 


80 


72 


67.0 


5.1 


65 


83 


60 


63.6 


6.6 


70 


100 


69 


80.9 


7.7 


61 


85 


68 


69.3 


6.9 


70 


84 


66 


66.3 


6.0 


58 


86 


62 


63.0 


7.1 



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46 INTEEFEEENCE AND ADAPTABILITY 

table for purposes of comparison. There are no errors to deal with 
as all misthrows had to be corrected by the subject. All figures 
used represent time in seconds. 

The curves as well as the tables show the interference effect and 
its relation to the practise effect, and indicate that the two associa- 
tions are becoming automatic. All the interference curves of all 
the groups show that the interference is present but that it is over- 
come, and that the associations are becoming automatic. This is 
true for every individual in all the groups, although the individual 
curves of Groups II. and IV. are not shown. 

In the alternate group the first sorting is about the same as that 
of the practise group. Among the women A t is 118 sec, A 2 is 123 
sec, while in the practise series it is 120 sec. Among the men A x is 
107 sec, and A 2 is 111 sec, while the practise group record is 117 
sec. But the practise curve drops very rapidly, especially among the 
men, while the alternate curve does not show rapid improvement. 
The practise curve is concave while the alternate curve is a straight 
line descending from about 96 sec to 72 sec. for the men. The 
women's curve is concave due to the very rapid improvement of the 
first day, after which it follows the men's curve closely. The rate 
of gain on the percentage basis is higher in the practise group than 
it is in the alternate group, being .36 for the men and .48 for the 
women in the practise group as compared to .29 and .37 respectively 
in the alternate group. 

There are no distinct plateaus except that of My during the 
fourth and fifth day. On the sixth day he makes rapid improve- 
ment though he is uniformly poorer than the average of the group. 
But this plateau does not mean no improvement, nor that interfer- 
ence annuls practise, for on the first day he ranges between 100 and 
115 seconds, while on the last day he remains between 80 and 90 
seconds. 

The first sorting of each day is decidedly quicker than any other 
and shows a decided drop in the curve. This decrease in time is be- 
cause of the fact that the first practise has no interference, while for 
the rest of the sortings the interference of the opposing arrangement 
is present. The good initial records of each day indicate where the 
curve would be were it not for the interference. This shows that the 
two associations are well established and that the interference of 
the previous day has faded away. The women have a better initial 
record than the men, yet their general curve is slightly poorer. 
There seems to be a greater discrepancy between what they could 
do without interference and with it than there is among the men. 
These initial drops however both among men and women become 
relatively less and less and are hardly noticeable on the last day. 



THE CABD-SOETING EXPEEIMENT 47 

This is because of the fact that the records of the whole day are 
down to the standard set by the initial records, and that the inter- 
ference has less and less influence. That they do not quite attain 
to the practise limit is obvious from the conditions of the experi- 
ment. When the change is made there is a temporary disadvantage 
to be overcome. This is often overcome in a few seconds, but it will 
always require a little time. There were individuals even in this 
group who sorted the eighty cards in 55 seconds, and for the entire 
sixth day did not go above 65 seconds. This is very near and in 
some cases below the practise limit. Em and Gr, although the poor- 
est of the groups, kept under 70 seconds for the entire sixth day. 

In Plates II. and III. and in Table V. we have the individual 
curves and records for Group III. The average curve is given in 
Plate IV. The average curves show three spires each day showing 
clearly the changes in arrangement. At the beginning of each day 
there is no rise of any account in the curve, which begins on the 
practise level of the previous day, no interference effect being re- 
tained. The first arrangement without interference attains as low 
a point in the curve as is attained on that day and with the women 
a little lower. Towards the last the best absolute time is made in 
the first four without interference, but this is very small and with 
some subjects nothing at all. It may be because of being perfectly 
fresh at the experiment. The curves show that the improvement is 
very rapid after the changes and that the same efficiency is reached 
as before. 

Although the women's practise curve is a little better than that 
of the men, their curve in Group III. is not quite so good, which is 
most plainly shown in the last few days by the drop in the men's 
curve. The men's curve surpasses their practise curve quite fre- 
quently but the women's does not, except at first. 

For the first three days the men rise higher after the change than 
the women, for the last three days they are about the same. In spite 
of this higher rise of the first three days and the equivalent rise of 
the last three, the men attain a greater efficiency than the women, 
shown by the fact that their curve comes lower than the women for 
the last sortings of each section. The four women in the lower sec- 
tion of Plate II. do not show the changes in arrangement so clearly. 
There were many cases where the last sorting of a section took longer 
than the first. Among the men there were very few cases where the 
second sorting of an arrangement took as long as the first; among 
the women there were many where it took longer. During many of 
the sections there is negative improvement among the women ; never 
among the men. Of course the women do not rise so high for the 
first sorting after the change but on the other hand they do not im- 



48 INTEBFEBENCE AND ADAPTABILITY 

prove so rapidly. The previous association seems to be made auto- 
matic by the men more quickly than by the women. 

The average curves show that by the second sorting the same 
plane of efficiency is reached as had been attained before the change. 
This allows the two remaining sortings to accumulate practise effect 
and reach a better level. The men 's curve passes that of the women, 
being a little higher on the first day, but on and after the second 
day it is lower than that of the women. Both among the men and 
the women the rise after the change becomes less and less, and is not 
nearly so great on the last day. 

The interference becomes less and less, the two associations be- 
come automatic, and need only the first sorting to reduce them to 
the practise level and overcome the temporary disadvantage. The 
improvement on the percentage basis for the first arrangement is 
.29 for the men and .27 for the women ; for the second arrangement 
.34 for the men and .25 for the women. The curves are slightly con- 
cave, nearly as much so as the practise curve, and in this are dif- 
ferentiated from those of the alternative group which are straight 
lines. The best record in Group III. was that of Ca, 44 seconds, 
which was one second less than the best in the practise group. Thus 
the best record is in the group having interference. 

Mrs. Sv and Mr. Sp are the only subjects showing plateaus in 
Group III. Sp makes no progress after the third day and is de- 
cidedly poorer on the sixth day. His performance on the first day 
averages about 110 sec. with a wide range, while on the last day he 
varies between 85 and 95 seconds. It is noticeable that at his best 
he rises high immediately after the change, while on the sixth day 
he does not rise so high, but neither does he reach such a low level. 

Mrs. Sv varies from 110 to 125 seconds at the beginning, but on 
the last day she ranges between 85 and 95 seconds. Though she 
makes the least improvement she by no means stands still. Often 
after the break she does nearly as well as and sometimes better than 
before, but her improvement is low within the sections and many 
times negative. 

The average records of men and women in Group IV. are shown 
in Plate V. The change to the second arrangement is very clearly 
shown every day while there is just a little rise at the beginning of 
the day. Here the record of the women is a little better than that of 
the men, due to the poor records of As among the men and to there 
being only three subjects. Moreover the work of Misses Mor and 
Ag was exceptional among the women. Miss Ag made the best record 
of the entire experiment, sorting the eighty cards in 42 seconds, and 
having many records below 50 seconds. After two or three days the 
time was as good for the second arrangement with interference ajs 



TEE CABD-SOBTING EXPEBIMENT 49 

for the first without it. As and Mrs. Th were much poorer on the 
second arrangement than on the first for the first three days, after 
which the two were about the same. In this group the men again 
seem to rise a little higher after the change but it is not nearly so 
pronounced as in Group III. 

Group IV. shows a higher rate of improvement than Group III. 
(.35 for both men and women in the first arrangement and .34 for 
both in the second arrangement). The curve is concave and is as 
good as the practise curve except immediately after the changes. 
Here we find a much more rapid automatization of both associations, 
and interference playing less and less a part. The interference 
effect of eight previous sortings seems no more than that of four. 
What relation the number of repetitions have to the interference 
effect will come up for discussion under the head of "Relation of 
Interference to Practise Effect." 

Bair asked the question whether the interference becomes greater 
with the number of practises of the previous association, 2 that is, 
whether a habit made more permanent with many practises offers 
more resistance than one formed by only one or a few practises. He 
found that the difference between the last sorting of the first series 
and the first sorting of the second is slightly greater with many 
repetitions of the first. He concluded, however, that this was due 
not to interference but to the decrease in the first order. His results 
showed that it took less time to make the associations in the second 
order after practising the first order many times than with only a 
few practises of the first order. 

Table VII. summarizes the results under this heading for all the 
groups. This gives us a change to the new order after one order had 
been fixed by one, four, eight, and forty-eight repetitions. The data 
of Group I. were obtained by having the subjects sort the cards into 
the second arrangement after their forty-eight sortings of the first 
arrangement. The data of the other three groups are the records 
of each group for the first sortings of each arrangement on the first 
day of the experiment. 

"We find that in Groups II., III., and IV., where one, four and 
eight sortings of the first order were given before changing to the 
second, the first performance of the second order takes longer than 
the first performance of the first order. But we find in Groups III. 
and IV. a more rapid improvement in the second arrangement than 
in the first. This is due to the transfer effect of the sortings of the 
first order. The higher rise then is due entirely to interference but 
the interference is very rapidly overcome. Bair found that with ten 

2 J. H. Bair, loc. cit., p. 37. 



50 INTEBFEBENCE AND ADAPTABILITY 

practises of the first order the second took 1 second less. Group IV. 
takes just four seconds more. Bair ha'd just half as many cards, so 
that the difference between his results and the present are very 

TABLE VII 

The upper column gives the first four sortings of the one arrangement, 
except in the alternating group, where only one could be obtained; the lower 
column gives the first four sortings of the new arrangement, except in Group II., 
where only one sorting could be obtained. 



Group I 
Men Women 
117 120 


Group II 
Men Women 
107 118 


Group 
Men Y 
118 


III 
fomen 
114 


Group IV 
Men Women 
101 93 


95 


105 




100 


101 


91 


78 


84 


101 




94 


97 


74 


75 


81 


104 




89 


93 


73 


69 






Change to New Order 








120 


107 


111 123 


132 


118 


104 


97 


102 


98 




108 


99 


87 


81 


93 


90 




98 


90 


82 


72 


86 


85 




92 


86 


76 


67 



small. In the practise group which had forty-eight sortings of the 
first order before changing to the second, the results tally with 
Bair's. The men's time increases just 3 seconds while that of the 
women decreases 13 seconds, which on the average (as Bair takes it) 
brings the time a little less for the changed order than for the first. 
In Group I. the women improve much more rapidly after the change 
than in the first four of the first order, but the men have about the 
same rate of improvement. 

TABLE VIII 



Group I 


Group II 


Group III 


Group IV 


Men Women 


Men Women 


Men Women 


Men Women 


60 53 


4 5 


43 25 


39 34 



Table VIII. shows, as Bair found, that the difference in time be- 
tween one sorting and another requiring antagonistic reactions is 
greater, the greater the number of sortings of the first arrangement. 
We find that the greatest difference is in the first group, the next 
greatest in the fourth group, the next in the third group, and only 
a small difference in the first group. The difference is greater with 
the increasing practises of the first order. But as shown above this 
increasing difference is due to the better records attained in the 
first order and not due to interference. 

These results fully agree with those of Bair, with the additional 
fact that the second arrangement shows greater rapidity of im- 
provement. 






CHAPTER IV 

Individual Differences 

1. Rate of Improvement 

An important question in both experiments is that of the amount 
and rate of gain. What is the rate of gain in the card sorting ex- 
periment when interfering associations are present as compared with 
that of simple practise? What is the rate of gain in the typewrit- 
ing experiment after the break as compared with that before? Are 
the differences among the group greater or less when interfering 
associations are present? 

Table I. gives the initial performance, final performance, abso- 
lute gain, and rate of gain in the typewriting experiment. Table 
X. gives the initial performance, final performance, absolute gain, 
and percentage of gain, for each of the arrangements in all the 
groups of the card sorting experiment. The accompanying table 
gives the averages, medians and variability of the several groups in 
both experiments. The variability is expressed by the Pearson co- 
efficient of variability. The group marked "Sectional gains of 
Group III." is obtained by finding the average improvement of the 
sections of four sortings of each arrangement. The difference be- 
tween the first and fourth sorting is divided by the first sorting. 
By taking the average of the twelve sections for each arrangement 
(there being two sections each day) we have a fair measure for pur- 
poses of comparison as to how much gain is made in the individual 
sections. This has no significance for the total gain, but it has value 
as a measure of the immediate rate of improvement when four 
repetitions of the previous association are present. The mediae is 
used for the purpose of comparing the groups and the average for 
the determination of the variability. Only in a few cases are the 
averages and medians different. 

We find that 28 per cent, of the men of the typewriting experi- 
ment reach or surpass the median of the women both before and after 
the break. In the practise group of the card sorting experiment 
25 per cent, of the men reach or surpass the median of the women. 
In the alternating series no men reach the median of the women. 
In Group IV. one third of the men reach the median of the women. 
These groups are however too small to warrant any conclusions as 
to sex differences. 

51 



52 



INTEBFEBENCE AND ADAPTABILITY 



Initial 

Performance 

A x A 2 

Wa 103 

Co 82 

01 100> 

Br 91 

Miss Sm 115 

Miss Co 85 

Miss Fo 127 

Miss St 104 

Em 85 95 

Gr 97 102 

My 108 113 

Mrs. Cu 100 108 

Miss Br 123 111 

Mrs. Mt 120 130 

Ca 83 92 

Si '. 100 120 

Dr 97 103 

Wi 93 102 

Sv 93 84 

Sp 119 126 

Ed 117 126 

Miss Br 118 110 

Mrs. Kv 103 111 

Mrs. Wo 86 83 

Mrs. Sv 122 116 

Mrs. Su 88 85 

Miss Th 102 98 

Mrs. Ao 90 86 

As 91 100 

Cu 75 76 

Bl 86 86 

Miss Mor 76 76 

Miss Ag 68 75 

Mrs. Th 95 86 



Av. 
Typewriting, before break ... .72 

Typewriting, after break 50 

Prelim. Group before break . . .67 
Prelim. Group after break ... .53 
Card-sorting Group III.— A t . .29' 
Card-sorting Group III.— A 2 . .34 



TABU 


3 X 










Group I 










Final 


Absolute 


Percentage 


Performance 


Gain 


of Gain 


A x 


M 


At 


M 


M 


A 2 


53 




50 




.48 




54 




28 




.34 




70 




30 




.30 




60 




31 




.34 




56 




59 




.52 




47 




38 




.45 




67 




60 




.47 




53 




51 




.49 




Group 


II 










60 


65 


25 


30 


.29 


.31 


65 


65 


32 


37 


.33 


.35 


83 


86 


25 


27 


.23 


.24 


67 


74 


33 


34 


.33 


.32 


76 


75 


47 


36 


.39 


.32 


70 


69 


50 


61 


.41 


.47 


Group 


III 










57 


65 


26 


27 


.31 


.29 


73 


73 


27 


47 


.27 


.38 


69 


68 


28 


35 


.29 


.34 


67 


65 


26 


37 


.28 


.36 


66 


63 


27 


21 


.29 


.25 


90 


89 


29 


37 


.24 


.29 


72 


67 


45 


59 


.38 


.47 


74 


70 


44 


40 


.37 


.36 


77 


81 


26 


30 


.25 


.27 


61 


60 


25 


23 


.29 


.28 


97 


91 


25 


25 


.20 


.22 


66 


66 


22 


19 


.25 


.22 


73 


70 


29 


18 


.28 


.18 


65 


65 


25 


21 


.28 


.24 


Group 


IV 










64 


68 


27 


32 


.30 


.32 


44 


47 


31 


29 


.41 


.38 


56 


56 


30 


30 


.35 


.35 


51 


51 


25 


25 


.33 


.33 


42 


47 


26 


28 


.38 


.37 


45 


58 


30 


28 


.32 


.33 


Men 






Women 




A.D. 


Med. 


Var. 


Av. 


A.D. Med. 


Var. 


.04 


.73 


4? 


.745 


.05 .76 


.58 


.07 


.50 


.99 


.57 


.07 .58 


.93 


.03 


.67 


.37 








.12 


.53 


1.59 








.03 


.29 


.55 


.27 


.03 .28 


.57 


.07 


.34 


1.20 


.35 


.04 .24 


.80 



.14 


1.25 


.12 


.04 


.10 


l.U 


.26 


.80 


.16 


.07 


.13 


1.75 


.25 


1.04 


.17 


.06 


.15 


l.J t 6 


.34 


.83 


-.48 


.02 


.48 


.29 


.29 


.75 


.36 


.05 


.35 


.83 


.35 


.67 


.34 


.02 


.34 


.34 


.35 


.33 


.34 


.02 


.34 


M 



INDIVIDUAL DIFFERENCES 53 

Sectional gains of Group III. 

A x without interference ... .16 .05 

A x with interference 25 .04 

A 2 23 .05 

Practise Group 36 .05 

Alternate Group 29 .04 

Group IN.-A 1 35 .04 

Group IY.-A 2 35 .02 

In Group III., however, there are seven men and seven women, 
and the interference effect is most clearly shown. Both in the abso- 
lute gain and in the percentage of gain Miss Br alone surpasses the 
median of the men in both arrangements. In A 1 Miss Th surpasses 
the median of the men. When it comes to sectional gains, Mrs. Su 
alone reaches or surpasses the median of the men in both arrange- 
ments, and Mrs. Ar surpasses their median in A x only. 

We find the women just a little ahead in the typewriting experi- 
ment but not sufficiently to cover the probable error. The variabil- 
ity of the two groups is about the same. Both the men and the 
women in the regular and preliminary groups have greater variabil- 
ity after the break than before. In the regular group of the type- 
writing experiment the variability after the break is 1.60 greater 
than before, and for the men 2.11 times as great as before. In the 
men of the preliminary group the variability is 4.3 times as great 
after the break as before. This index of variability shows greater 
differences in improvement when an old association is persisting 
than without interfering associations. The trend of the entire series 
of experiments emphasizes this greater variability under conditions 
of interference. 

Another significant fact of the rate of improvement in the type- 
writing experiment is the lack of correlation between the rate of 
improvement after the break and before. Were there such a corre- 
lation it would indicate that the differences found after the break 
are simply due to the ability of the subject to improve by practise 
as the simple practise curve shows. Among the men of the prelim- 
inary group there is a negative correlation of — .86 (P.E., .05) ; 
among the men of the regular group a correlation of .13 (P.E., .19) ; 
and among the women a positive correlation of .45 (P.E., .17). This 
indicates that the ease and rapidity of improvement after the break 
is not exclusively due to the same ability as the improvement before. 
The astonishing fact is that some of the writers before the break, 
who expected to make great progress after, did not nearly measure 
up to their expectations, while others did a great deal better after 
the break than before. CI was the most rapid writer before the 



54 INTEBFEBENCE AND ADAPTABILITY 

break, but did very poorly after it. On the other hand Ru who had 
very poor records before the break became considerably more effi- 
cient after it and did not seem to be much disturbed because of the 
change. Of course a negative correlation of — .86 is exceptional, 
but the tendency seems to be practically no correlation. 

Under the study of relapses is brought out the fact of correla- 
tion between efficiency in improvement and avoiding mistakes, which 
is also important as an index of individual differences. 

In the card-sorting experiment we find but little difference as to 
variability in the rate of improvement. The men are more variable 
in the simple practise, and less variable in the alternate and sec- 
tional measures of Group III. These are the only well-defined sex 
differences. In both these groups the improvement is greater among 
the women than among the men. As would be expected the im- 
provement in the practise group is greater than in the alternating 
group, the difference being .07 for the men and .12 for the women. 

In Group III. the rate of improvement is higher than it is in the 
alternate group. This is especially true of the second arrangement 
which is continually subject to interference. The differences are 
greater in the sectional measures of the four sortings of each ar- 
rangement. These measures are the average rate of improvement 
for the sections of four sortings. Here the median percentages under 
interference are for the men .26 in A t and .25 in A 2 ; and for the 
women .13 in A t and .15 in A 2 . Since this sex difference is greater 
than the sex difference in the total rate of improvement, the men 
must rise higher in the curve after the change and thus be able to 
improve more rapidly. This is the actual fact and explains the 
more rapid gain. The curves of Plate IV. show that the men drop 
lower with practise and rise higher immediately after the change. 
But this fact is still more clearly shown by the actual difference in 
time between the last sorting of the one arrangement and the first 
sorting of the next. This difference is 15 to 20 seconds greater for 
the men than for the women. This explains the fact that in the 
sections the men's rate of gain on the percentage basis is about twice 
as large. After the third day the men do not rise much higher im- 
mediately after the change, but they improve more than the women. 

This greater immediate interference among the men does not 
seem to the writer to indicate that four sortings have a greater inter- 
ference effect on the men than on the women. The men and women 
who had the least rise after the change had the poorest records, 
while those who rose high also dropped very low. With the poorer 
ones neither association seems so well fixed. Mrs. Su and Ar, who 
made the best records of the women of Group III., rose very high 



INDIVIDUAL DIFFERENCES 55 

immediately after the change, but improved rapidly. Miss Ag, who 
had the best time of any subject, rose very high after the change, 
but showed rapid improvement. Mrs. Sv and Ku who had the poor- 
est records among the women of Group III., did not rise high, in 
fact, often did better right after the change than on the fourth sort- 
ing, thus giving a negative rate of improvement. It does not seem 
true that interference has the most lasting effect on those on whom 
it shows up strongest immediately. 

The indication of the experiment is rather that those who rise 
highest after the change can most easily overcome the interference. 
It seems to the writer that interference effect must be measured by 
its persistency, and that those in whom it persists the longest are the 
most subject to interference. If this is true, the women of Group 
III. are less able to overcome the interference than the men. The 
men show a greater immediate effect but it is rapidly overcome. The 
reason the men can overcome the retarding effects of the previous 
associations more fully is because the two associations are more 
firmly fixed and more nearly automatic, so that a few sortings will 
raise the association to its previous efficiency. But why should the 
men show this greater immediate and momentary interference ? Be- 
cause of the fact that both associations are more firmly fixed and 
will when in full play require more energy to be displaced and give 
the momentary advantage to the other association. These higher 
rises indicate better fixed and more automatic associations, and the 
smaller effects of the change indicate less well fixed associations. 
When an individual on the fifth or sixth day of the experiment fails 
to improve with four sortings, the indications are that both associa- 
tions are weak. When an individual however shows a great im- 
mediate effect but a rapid gain, it indicates that both associations 
are well fixed. The interference has the greatest effect where no 
associations are well fixed, for it is the cause that neither is well 
fixed. With the other individual, interference is an incident, but 
not fundamental. The fundamental thing is the fixing of the two 
associations. 

Through the entire group the individuals that improved most 
and reached the best absolute time were those that rose high after 
the change but improved rapidly; those who improved least for the 
whole experiment and who did not reach the level attained among 
the others, were those who did not rise high nor improve rapidly. 
If the above explanation be the correct one, the men's associations 
are better fixed and interference has less influence over them. 
Their improvement in the sections is twice as great, the first per- 
formance after the change is 15 to 20 sec. poorer than that of the 



56 INTEBFEBENCE AND ADAPTABILITY 

women, and they reach absolutely lower levels. These differences 
are also true within the groups. 

I do not however think that we are justified in drawing any 
sweeping conclusions as to sex differences on this point. Aikins 1 says 
that men have a greater tendency than women to form habits and 
use them, to build them together and to build one on another, to re- 
construct the personality on the basis of habit. This he calls a truly 
secondary sexual characteristic and it is one of the arguments why 
woman is more primitive than man. Building up a personality on 
the basis of highly elaborated and varied habits is certainly a cri- 
terion of development. Well-fixed associations would indicate a 
higher stage of organization, and a greater freedom from overpow- 
ering interference than weak associations on which the interference 
would have great effect. The men in the experiment seem to have 
better fixed associations, a set of habits better developed, than the 
women have. The experimental results agree with the contention 
of Aikins. If these conclusions are correct we should expect men 
to have stronger habits and associations, and better able to build up 
the personality on the basis of habit. With them interference would 
have less effect. Interference would have a greater effect on the 
women. The men should therefore be better able to adapt them- 
selves readily to the variations which the environment presents. 

It must be borne in mind, however, that the sex differences here 
are not large, not nearly so significant as the individual differences 

among both men and women. 

i 

2. Initial Efficiency and Plasticity 

One of the interesting questions of individual differences in 
mental traits is that of the relation between initial efficiency and 
susceptibility to improvement by practise. Does a high initial effi- 
ciency indicate a greater ability to profit by practise or does it indi- 
cate that the individual is farther along on his practise curve, and 
therefore, not so susceptible to improvement by further practise? 
Conversely, does low initial efficiency indicate less ability to im- 
prove by practise, or is the slow individual simply not so far along 
on the curve and therefore susceptible to greater improvement? 
F. L. Wells la asks the question thus: "Is high initial efficiency a 
product of greater amount of practise, or of greater ability to profit 
from practise, and conversely, a low initial efficiency the product of 
lack of practise or of little ability to profit from practise? As the 

1 H. A. Aikins, "Man, Woman and Habit," Psy. Bull, 5, 50, 1908. 
A « F. L. Wells, ' * Eelation of Practise to Individual Differences, ' ' Am. Jour. 
Psych., 23, 75, 1912. 



INDIVIDUAL DIFFERENCES 57 

first or second of these alternatives hold true we may expect less or 
more improvement by the more efficient." 

Wells conducted practise experiments on men and women in a 
simple addition test and in a number checking test. With few ex- 
ceptions the curves do not cross. Those having the highest initial 
efficiency have the highest final efficiency, and those with the lowest 
initial efficiency have the lowest final efficiency. There is a fair 
correlation between the relative positions in initial and final effi- 
ciency. He concluded thus: ''We are confronted then with cases 
indicating a high initial efficiency as a manifestation of superior 
ability to profit by practise, or plasticity ; and on the other hand with 
cases exhibiting a low initial efficiency with minor possibilities of 
practise improvement. ' ' 2 

A high correlation exists between the initial efficiency and final 
efficiency in the card sorting and typewriting experiments, and in 
the card-sorting experiments there is a correlation between the 
initial efficiency and the rate of improvement. This shows that not 
only are those with highest initial efficiency able to improve as much, 
but even to improve more. With this it must also be borne in mind 
that those with poor initial reeords tend naturally to get a high per- 
centage of gain. 

In Group IV. of the card-sorting experiment there is a perfect 
correlation in relative initial and final position in A 1 and A 2 among 
both men and women. There is also perfect correlation between 
initial position and rate of improvement in both A 1 and A 2 among 
both men and women. These figures are all given in Table X., which 
show initial and final efficiency and rates of improvement for all 
the subjects. 

In Group II. there is a perfect correlation between the relative 
initial and final positions of the first arrangement among both the 
men and the women. In the second arrangement the Pearson coeffi- 
cient for the men is 1.00, and for the women .50 P. E. .29. • The 
men have a correlation of .50 P. E. .29 between the initial efficiency 
and the rate of improvement in both arrangements. There is no 
correlation between the initial efficiency and rate of improvement 
among the women. 

In Group III., with seven men and seven women, the correlation 
between the relative initial and final position of A 1 is .96P.E. .02 
for the men, and .93P.E. .03 for the women. In A 2 it is .89P.E. 
.05 for the men, and .96 P.E. .02 for the women. Between the initial 
efficiency and rate of improvement of A ± the correlation for the men 
is .43 P.E. .20. Only one man and 2 women out of the fourteen 

2 Wells, loc. cit., p. 81. 



58 INTERFERENCE AND ADAPTABILITY 

subjects are out of their relative position, though there is not much 
correlation between initial position and rate of improvement. The 
outstanding exception among the men of Group III. is Rd, who has 
the poorest initial record but whose rate of improvement is highest. 
His low initial record seemed to be due to a peculiar nervousness 
and hesitancy. He soon seemed at ease in the experiment. He was 
the only subject showing a very poor initial record and high im- 
provement. 

Among the women of the practise group there is perfect corre- 
lation between the initial and final efficiency, but none between the 
initial efficiency and rate of improvement. Among the men of the 
practise group there is no correlation between relative initial and 
final position. Wa is the poorest at the beginning and the best at 
the close. 

If we take the results of the two arrangements of Groups II., 
III., and IV., and the one arrangement of Group I., we find a total 
of 60 cases of initial performance with a practise of 48 repetitions. 
Out of these sixty only eight curves cross any others. Six of these 
eight cross only one curve, one crosses two, and one crosses three. 
Of the six who end just a little better than the one starting next be- 
low them three of them are only one second lower. This makes it 
almost universal with the cases in hand that a higher initial effi- 
ciency goes with a higher final efficiency and a lower initial efficiency 
with lower final efficiency. 

We find the most significant exception to this in the practise 
groups. Among the men of the practise group there is no correla- 
tion. In none of the practise groups is there correlation between 
initial efficiency and rate of improvement. In all the groups having 
interference we find high correlation between relative initial and 
final position, and some correlation between initial efficiency and 
rate of improvement. In Group IV. it is perfect both among the 
men and women. In Group III. the correlation is high for relative 
position and .68 between initial position and rate of improvement 
pi the first arrangement for both men and women. In Group I. 
there is high correlation in relative position and .50 between initial 
position and rate of improvement for the men in both arrangements, 
for the women. We find a higher correlation between initial and 
final efficiency in the interference groups than in the practise group. 
We also find no correlation in the practise group between initial 
position and rate of improvement, while we do get several appreci- 
able correlations in the interference groups. It seems then in a test 
such as the card-sorting experiment, which demands a high degree 
of attention and quick discrimination, the most efficient are suscept- 



INDIVIDUAL DIFFEEENCES 59 

ible to not only as great but even to greater improvement than the 
less efficient at the beginning. And when interference is continu- 
ally present there is still a higher correlation between plasticity and 
initial efficiency. Not only are the more efficient able to improve 
more in pure practice but when the opposing factor of interference 
comes in their ability comes still more clearly to light. This corre- 
lation of the plasticity of the individual, his ability to adapt him- 
self to the new situations and overcome the ever-present interference, 
with his initial ability is significant, and gives a clearer and more 
pronounced index of individual efficiency than the simple practise 
curve can ever give. 

Table I. gives the initial and final performance of the typewrit- 
ing experiment both before and after the break. "We find some 
correlation between the initial and final efficiency, both before and 
after the break. In the preliminary group the eight men have a cor- 
relation of .95P.E. .02 before the break, and .76P.E. .09 after it. 
Among the men of the regular group it is .96P.E. .02 before the 
break and .43 P.E. .20 after the break. Among the women the corre- 
lation is .60 P.E. .14 before the break and .50 P.E. .17 after the 
break. There is no correlation worth mentioning between the initial 
position and rate of improvement. Here we find a distinctly higher 
correlation before the break than after it. The correlation among 
the men is higher than that of the women. The smaller correlation 
after the break is due to the greater variability of improvement 
which we found after the break. This shows that the break has a 
very great initial effect on some, but is soon overcome, while others 
do not show such a great immediate effect but a more persistent 
one. This same thing is shown by the relapses, rate of improvement 
and variability, and is clearly seen in the curves. 

3. Errors as a Cause of Interference 

Most investigators of the practise curve have pointed out* the 
grouping and individual differences in errors. Yoakum says : ' * Per- 
haps the most noticeable individual difference is in the errors and 
their grouping. They were nearly always found in well limited 
groups with periods free from errors. 3 Swift and Schuyler also 
pointed out that the errors come in bunches and that there are long 
periods without any errors. 4 Book says that there is a direct corre- 
lation between the errors and the fluctuations of attention. 5 Again 

3 C. L. Yoakum, "Experimental Study of Fatigue," Psy. Eev. Mon. Supp., 
46, 77, 1909. 

4 Swift and Schuyler, "The Learning Process," Psy. Bull, 1, 310, 1907. 

5 Book, "Psychology of Skill," University of Montana Publications, 1, 118. 



60 INTEBFEBENCE AND ADAPTABILITY 

he says, ''blunders, false associations, and bad habits are liable to 
(repetition. ' ' 6 

Outside of these remarks there is 'no analysis of these groupings 
of errors. What is the nature of the groupings? Are there various 
kinds of errors or repetitions of the same error? Are there individ- 
ual differences and if so what is their relation to the general per- 
formance? What is the cause of the grouping, and why is this 
cause not operating during periods that are free from errors ? Book 
continually hints at something which may give a clue but which he 
does not develop. He uses such expressions as ''interfering habits, 
associations, and tendencies," "bad associations," etc., very fre- 
quently throughout his discussion of errors. These interfering as- 
sociations and tendencies may have a very important bearing upon 
the grouping of errors with reference to their nature and effects. 

TABLE XI 

For explanation of table, see text. 

1 2 3 4 5 6 7 8 9 10 11 12 13 15 20 
Women : 

Ha 51 25 10 2 

4 3 1 111 

Mo 27 8 1 1 1 

1 1 2 
Ta 22 9 2 

2 1 1 
Hf 11 3 

1 

McC 34 28 29 4 1 1 1 

3 2 1 2 2 12 
Wa 36 23 4 1 1 11 1 

4 2 1 1 

Wh 10 1 

Og 23 8 1 1 

g 3 1 

Gr 31 3 4 2 1 

1 1 1 

Men: 

CI 22 11 1 

3 

Ru 22 13 5 2 

5 1 

Ha 43 21 10 5 1 2 

7 2 1 1 

Br 27 1 

1 

De 25 7 1 1 

1 1 

La 31 7 1 

2 1 

McC 20 22 5 

1 1 1 

6 Book, loc. cit. } p. 82. 



INDIVIDUAL DIFFERENCES 61 



9 10 11 14 15 26 30 













TABLE XII 






For explanation of table, see text. 




1 


2 


3 


4 


5 


6 7 8 9 1C 


Women : 
Ha .... 


... 1 








1 




Mo .... 


.. . 4 


1 


1 






1 


Ta . . . . 


... 4 


1 






1 




Hf .... 


... 6 




2 

1 








Wa 


...25 


11 




3 




1 


McC ... 


...19 


5 


4 
1 


5 
1 


1 


1 


Wh .... 


... 2 












Og .... 


... 11 


1 


2 


5 




1 1 

1 


Gr .... 


...15 


3 


4 
1 


3 


1 


1 
1 


Men: 
CI 


... 5 


1 


3 




1 




Eu 


... 8 


2 




1 


1 




Ha .... 


...13 


6 


2 


1 
1 


2 




Br .... 


...15 


2 


3 


2 


1 
1 




De .... 


...11 


2 


3 








La .... 


...12 


3 










McC ... 


...25 


7 


1 









Table XI. gives the actual grouping of errors among the seven 
men and nine women of the regular typewriting experiment* I 
omit the eight men of the preliminary experiment because of the 
slightly different conditions. The errors given are those committed 
in the learning process during the 130 repetitions before the break. 
They do not include errors of omission for the key may have been 
struck but not hard enough to register. Nor do they include repe- 
titions of the correct letter for that may often be due to a superabun- 
dance of movement especially in the early stages. Only where a 
wrong letter is struck is the error counted. 

The figures in the upper horizontal column record one thing and 
those of the lower horizontal column another thing. The upper 
horizontal column gives the number of trials or repetitions which 



62 INTEEFEEENCE AND ADAPTABILITY 

contain a given number of errors. The figures at the top of the 
table give the number of errors in a trial, and the figures in the 
horizontal column give the frequency of the trials containing that 
number of errors. To make it perfectly clear the table shows that 
the first woman, Ha, has 51 trials each containing one error, 25 trials 
each containing two errors, 10 trials each containing three errors, 
etc. It will be remembered that there are 21 letters to be struck in 
each trial, and that there were 130 trials. If the horizontal column 
be added we have the total number of trials containing errors. If 
the figures of the column be multiplied by the number of errors 
they contain and their products added we have the total number of 
errors. The tables are not intended to show the totals so much as 
the distribution. 

Turning now to the second horizontal column of the table we 
have another fact expressed. In reading this part of the table the 
figures at the top of the table give the number of successive trials 
each containing one or more errors. The figures of the horizontal 
column give the frequency of such groups of successive trials con- 
taining errors. Turning again to Miss Ha we find that she has 
four groups in which three successive trials contain errors, three 
groups where four successive trials contain errors, and one group 
each of eight, eleven, thirteen, and fifteen successive trials, all con- 
taining errors. This shows the tendency of the subjects to have a 
run of errors in successive trials. In this column no figures are given 
under 1 and 2 because one or two trials does not give a succession 
of trials. Table XII. gives the grouping of the relapses after the 
break in the same way. 

Turning now to the upper horizontal column we find great dif- 
ferences in the number of errors per trial. Miss Wa has trials con- 
taining eight, nine, and eleven errors each. Br and Miss Wh have 
only one trial with more than one error. All the subjects except 
Mrs. McC have a majority of their trials with only 1 error each, 
Mrs. McC has 34 trials with 1 error and 64 with more than one 
error. The total number of errors varies from 13 for Miss Wh to 
207 for Mrs. McC ; the men vary from 29 for Br to 152 for Ha. The 
number of trials in which the errors occur varies from 11 for Miss 
Wh to 98 for Mrs. McC ; while the men vary from 29 for Br to 82 
for Ha. We find that some have an average of over two errors per 
trial while with others it is just a little over one. The variation is 
about 2 to 1. 

Turning now to the lower horizontal column which gives the fre- 
quency with which a succession of trials with errors occur, we find 
more marked individual differences. Miss Wh has no groups. Br. 






INDIVIDUAL DIFFERENCES 63 

De and Mrs. Hf show each one group of three successive trials con- 
taining errors, and De shows one of four. On the other hand Miss 
Ha has separate groups of thirteen and fifteen lines containing 
errors, while Mrs. McC has a number of eight, nine, ten, and eleven 
successive trials. McC has one group of twenty successive lines 
with errors while Ha has one of thirteen. This shows the tendency 
of errors to repeat. When some individuals make a mistake in one 
repetition the succeeding repetitions are liable to have errors, with 
others this is not so true. The table shows the extent to which it is 
true among the subjects. 

Table XII. gives the same information for the relapses. The same 
facts here are evident though in not so pronounced a form. Here 
there are of course only fifty trials, and the totals are not nearly so 
large. Miss Wa and Miss Og show about the same number of re- 
lapses, but Miss Og in about half as many trials. Miss Ha with 
only six relapses has five of them in one trial. Some average three 
relapses per trial others only one. Turning to the second horizontal 
column we find that Miss Wa has an extraordinary repetition of 
relapses, having thirty consecutive trials with relapses. McC has 33 
trials containing relapses, but 23 of these come in succession. Mrs. 
McC has 31 trials containing relapses and 31 of these come in 
groups. Miss Gr has 24 of her 27 trials containing relapses in 
groups. Others have no groups. This shows the tendency of one 
relapse to bring others in the succeeding trials. 

It seems to the writer that there is a fundamental difference be- 
tween the two kinds of grouping shown in the tables. The one kind of 
grouping is that of several errors in the same trial, the other that of 
a number of successive trials containing for the most part only one 
or two errors each, but repeated for many trials. The records as 
well as the introspections show that one error tends to cause another. 
This is what Book means when he speaks of "bad associations," 
"bad tendencies" and "interfering habits." Errors are* not 
grouped merely by chance, but an error makes an interfering as- 
sociation which is hard to overcome. The cause of the grouping of 
errors is due to these bad and interfering associations. Book finds 
that in some cases it takes a very long period of time for them to 
drop out, and that not until they do drop out can there be unim- 
peded progress. He cites the case of a music teacher who recom- 
mends that in learning to play a piano, it is better to practise in 
periods of 15 minutes with recesses, than to continue for an ex- 
tended practise, because of the fact that interfering tendencies do 
come in and cause error. When these drop out gain can be made 
without the strain and useless labor that would be expended in a 



64 INTEEFEBENCE AND ADAPTABILITY 

long practise at the time. This accounts also for the little improve- 
ment on some days and the smooth progress made on other days. 

Where many errors occur in the same trial we have what I shall 
term "general" interference due to the bad association. A wrong 
reaction may bring on four or five incorrect reactions, none of them 
a repetition of the first but all different and due to a sort of con- 
fusion brought on by the first error. Many observations show that 
a single error destroyed the freedom of movement, broke up the 
general association connection, misplaced the confidence of the sub- 
ject, and had a general inhibiting effect, causing various errors in 
the same trial. Often the subject would completely recover and on 
the following trials make no errors or only incidental ones. 

But where a wrong reaction occurs in a given trial and is re- 
peated in the succeeding trials, giving us a large group of lines con- 
taining the same errors, we have "specific" interference of the bad 
association. Miss Ha made one wrong reaction 18 and another 22 
successive times on the same day, while generally she made compara- 
tively few errors, and at no time did she make many errors in one 
line. She was told that she was making an error, but never sus- 
pected what it was and was surprised at the result at the end of the 
experiment. This is a very pointed case of "specific" interference, 
and yet never does the repeated error show any bad effect in the 
general sense upon the other reactions of the same trial. The same 
subject made only six relapses. Immediately after the break she 
arose to the situation, but other errors crept in and persisted without 
correction to the end. The table shows that she had many repeti- 
tions of the same error. 

On the other hand, Miss Wa has many trials containing 2, 3, 
5, 8, 9, and even 11 errors, but no repetitions in successive trials 
until after the "break" one relapse repeats itself a number of 
times. One error may upset her for the whole trial, causing great 
confusion, lack of confidence, slowing up of speed, deranging the 
association and generally inhibiting the work. There may be errors 
in the next line but not necessarily a repetition. She has a very 
marked general interference of the error but no specific interfer- 
ence. 

Hf of the preliminary group (no table is here given for them) 
made more errors than any other subject, but the effect of an error 
was not specific but general, nearly always bringing others. He 
had hardly any trials with only one error. Ja of the same group 
did not show general interference but specific, once having a run 
of 17 repetitions of the same error. 

McC presents a marked case of specific interference with a gen- 



INDIVIDUAL DIFFEBENCES 65 

eral inhibitory effect which lowered his speed. After the "break" 
he had a run of 26 relapses and before the "break" a run of 13 
repetitions of an error. This error and relapse did not cause other 
errors for he rarely made more than 2 errors or 1 relapse in a trial. 
The former habit had apparent control of this particular reaction, 
for after each relapse he would say he had made a mistake but did 
not know what and did not think it was the same one as before, 
being quite surprised later to find out that it was.- The error 
seemed to make him very deliberate. The observer could in prac- 
tically every trial see him about to strike the relapse number, then 
shake his head and strike the correct one. Sometimes he was about 
to strike the wrong one several times. Many times he would 
hesitate, even moving his fingers several times before striking, al- 
though he had the right reaction in mind. He said that his inhibi- 
tions were very strong and that he could not attain great speed on 
account of the mistakes. We see here that the specific interference 
had great control over him while the general effect was to increase 
his time but not to cause errors. 

These bad associations take many forms. In writing the three- 
place numerals inversions often occur. There are repetitions. 639 
was repeated instead of 628, the "6" giving the cue to the previous 
association. Sometimes the "3" of 853 was changed to "1" fol- 
lowing the association of the "1" with the "5" in the previous 751. 
Sometimes also a number farther on was placed back and then cor- 
rectly repeated in its proper position. Most of the errors however 
are the association of an absolutely wrong number with the reac- 
tion and then its repetition. 

The individual differences in grouping may seem to be minimized 
by the fact that those making the greatest number of errors are 
those having more errors per trial and more groups of successive 
trials containing errors. This is of course what will happen from 
the law of averages. But why do some make more errors than 
others? And why do the errors tend to form such groups? We 
can not separate all the factors which go to causing errors in the 
learning process. But one of them seems clearly to be this general 
and specific interference. An error is likely to happen for some 
cause or other, but whether that error will cause others or not may 
be a matter of individual difference. The evidence at hand seems to 
point to that conclusion. With some individuals an error does not 
seem to have bad interfering effect, with others it has a general 
interference effect, with still others a specific effect. That they both 
operate to some extent is evident, but that one operates more 
strongly in one individual and the other in another, is also evident. 



66 INTERFERENCE AND ADAPTABILITY 

The fact that there is no correlation between the errors and relapses 
shows individual differences in meeting one kind of interfering as- 
sociations which are not the same as those meeting another kind of 
interfering associations. 

The overcoming of such interference is important in all forms 
of the learning process. Much of the delay and lack of progress, 
and to a large extent the plateaus themselves, are due to such a 
combination of bad associations and tendencies, which must be over- 
come. Whether their effect be to cause general confusion and lack 
of control or repetition of the specific error, they must be reckoned 
with. Suffice it to say here that a closer analysis of errors is needed 
for the purpose of offsetting their bad effects. 

4. Variability 

The variability is greater when interference is present than 
under performance without interference. Table XIII. gives the 
medians of the average deviations in the card-sorting experiment for 
the men and women. 

TABLE XIII 





Practice Groups 
Med. P.E. 


Group II 
Med. P.E. 


Group III 
Med. P.E. 


Group IV 
Med. P.E. 


Men . . . 


... 4 1 


8 2 


7 1 


9 1.5 


Women 


...7 1.5 


4 1 


9 1 


5 1 



In Groups II. and IV. there are only three subjects of each sex. 
In each group one of the men was very much slower, while the women 
happened to be quite uniform. So the figures for those two groups 
can not be considered of great value. In Group III. however there 
were seven subjects and consequently the results are much more re- 
liable. With the exception of the women in Groups II. and IV., 
each of the interference groups show higher variability than the 
practise group. 

When we turn to the percentage rates of improvement the varia- 
bility becomes more significant. In the typewriting experiment the 
variability as expresed by the Pearson formula 7 before and after the 
break is as follows : 

Eegular men 47 before break .99 after break 

Preliminary men 37 before break 1.59 after break 

Women 58 before break .93 after break 

Gross variability 

7 Pearson formula, —— . This is the form as modified by 

V Average 
Professor E. L. Thorndike. See ''Theory of Mental and Social Measurements, ' ' 
1904, p. 102. 



INDIVIDUAL DIFFEEENCES 67 

Nor do these rates of improvement correlate, showing that those 
improving fastest before the break do not improve most after it. The 
correlation figures are : Men, preliminary group — .86 P.E. .06, men 
regular group .13 P.E. .19; women .45 P.E. .17. 

This variability is further emphasized by the fact that those ma- 
king the most relapses have the slowest rate of improvement, as 
shown by the following correlations. 

Between Relapses and Eate of Improvement 

Men, regular group r = —.76 P.E. 10 

Men, preliminary group r= —.69 P.E. 12 

Women r= — .09 P.E. 28 

In the card-sorting the same thing is true. Table XIV. gives the 
variability as expressed by the Pearson formula for each of the 
groups, for both men and women. 

TABLE XIV 

Practice 
Group Group II Group III Group IV 

Men, A x 83 .75 .55 .67 

Men, A 2 1.20 .33 

Women, A x 29 .83 .57 .34 

Women, A 2 .80 .34 

One subject among the men of the practise group brings the rate 
to higher than normal — Wa, who is the only subject of the entire 
series to begin as poorest and end up as best of the group. His first 
records were so phenomenally high as to make it purely accidental 
in that group. The rest of the table uniformly shows greater varia- 
bility under interference. 

In the discussion under plasticity the figures are given to show 
greater differences in plasticity under interference than in the simple 
practise curve, and consequently higher correlation between initial 
efficiency and final efficiency and between initial efficiency and rate 
of improvement. 



CHAPTER V 

Discussion and Summary 

1. Method 

Munsterberg 1 pointed out three experimental conditions for the 
investigation of his problem. They were: (a) The movements must 
be entirely mechanical so as not to call in the attention, (b) They 
must be easily varied, (c) They must call in the attention when- 
ever a false movement is made or whenever the old habit returns. 
Because of the first requirement he held that the experiments could 
not be performed in the laboratory. The card-sorting experiment, 
it seems to the writer, meets all the conditions for the investigation of 
the problem of interference and meets them more decisively than his 
experiments do. It meets the needs of an experiment better because 
it can be more strictly measured, because it brings out greater possi- 
bilities of interference, and because it requires the maximum of at- 
tention. 

In this experiment we have exactly similar conditions for each 
individual with reference to the number of repetitions, which would 
not be possible in an experiment of the kind described by Miinster- 
berg. It means more exact measurement and makes possible a study 
of individual differences. In the second place the changes, coming 
quickly as they do, and requiring the exclusion of the ten former 
associations, give greater opportunity for interference to show its 
full force. Not until we know the full force of the interference are 
we ready to get any results of the overcoming of that interference. 
When a watch is changed to another pocket and the number of wrong 
reactions counted, there are a number of things which might affect 
the number of wrong reactions. The pressure of the watch in the 
other pocket, the accidental moves to that pocket, a lack of record 
of the number of times the watch was actually sought during the day, 
the varying conditions from day to day, leave a possibility that in- 
terference does not get its full play or at least gets a varying oppor- 
tunity. By the immediate change of arrangements and by an equal 
number of repetitions in a given length of time this factor is better 
controlled. 

This experiment requires the maximum of attention. The cards 

1 Hugo Munsterberg, loc. tit., p. 71. 

68 



DISCUSSION AND SUMMARY 69 

do not come in a given order and consequently there is no chance to 
grow lazy on the habit. There must be eighty individual discrimina- 
tions and as many reactions. Attention did not waver in the card- 
sorting experiment as it sometimes did in the typewriting experi- 
ment. It continually calls the discriminative powers into play, but 
in the most simple form, a simple stimulus and its consequent reac- 
tion. The stimulus is not given until the card just above the one in 
question is thrown, and consequently the conditions for each are ex- 
actly the same. The point for which Miinsterberg contended was 
that attention could not be centered on the performance before it 
was to take place. That condition is met here because the stimulus 
is not perceived until it must be acted upon. 

The card-sorting experiment, it seems to the writer, is somewhat 
better than the typewriting experiment for the problems here in- 
vestigated. The typewriting experiment, while perfectly valid, has 
two hindrances. In the first place there is such a difference between 
individuals in skill in manipulating a machine as to minimize the 
individual differences of the experiment. In the present experi- 
ment this factor has not been of such great importance because the 
results show that there is no correlation between the native skill on 
the typewriter and the ability to break the habit. 

In the second place the gain on the typewriter is so great because 
of the poor initial performance, which in turn is caused by the fact 
that the subjects are awkward on the machine. This high initial 
record makes the retardation after the break seem small. After the 
break the subjects are familiar with the machine and can make fairly 
good records as compared with their initial records. The interfer- 
ence is clearly shown but not in the proportion which it really holds. 
Only in a few cases was the first performance after the break abso- 
lutely poorer than the first performance in the practise curve be- 
fore the break. On the other hand in the card-sorting experiments 
the interference of the first four or eight sortings always made the 
time of the first sorting of the new arrangement longer. But there 
was no such great general transfer effect as in the typewriting ex- 
periment. If all the subjects were used to handling a machine the 
same thing would undoubtedly be true in the typewriting experi- 
ment. 

The criticism has been made that the cards did not come in a 
given order. It has been held that the cards should be arranged in 
a given order for each ten, for example, 9, 1, 7, 2, 10, 6, 4, 8, 3, 5 for 
the first ten and then the same order repeated for every ten through 
the eighty cards. The subject could then learn this order and the 
arrangement and of course reach a better absolute time record than 



70 INTERFERENCE AND ADAPTABILITY 

in the present experiment. This would miss the purpose of the ex- 
periment. A chance order with no card repeating itself successively 
is the ideal for the purpose. Under 'the proposed scheme one would 
substitute units of ten for the single units. We have in the eighty 
cards just eighty repetitions of what would happen if a single stim- 
ulus appeared in a tachistoscope and a definite reaction was made, 
because each single card is seen only after the one above it is re- 
moved, and the entire process occupies in the later stages about three 
fourths of a second and with some was reduced to nearly one half 
second per card. The total time gives the measurement of eighty 
such simple reactions, each one under exactly the same conditions. 
Sorting the cards in sixty seconds means that it is practically auto- 
matic, or three fourths of a second is the automatic limit. If a 
change is then made to the other arrangement and the total time goes 
up to 80 seconds and one second is the measure of a single reaction. 
If in the second sorting the time is again sixty seconds we have a 
measure of the interference and the rapidity with which it is over- 
come both for the total and for a single reaction. The eighty cards 
thus arranged leave little room for error, which would not be the 
case with a single reaction. 

Bergstrom, Bair, and Beazley used pictures on their cards, and 
Beazley used pictures on the keys of his instrument. The pictures 
which they used seemed not to be of equal difficulty nor can they be 
of equal familiarity. Bergstrom even used cards with a different 
picture on the other end. This it seems to the writer can not help 
being a disturbing element. Cards with numerals or letters or some 
other such simple stimuli should be used. 

Bergstrom 2 allowed an interval of two minutes between the alter- 
nate sortings, or nearly two minutes depending on the length of time 
the sorting took. He had previously found that about two thirds of 
the decrease in the amount of interference took place in the first 
minute. How long an interval should be given between the sortings 
is therefore a very important factor. That he should find the inter- 
ference effect so great after an interval, when according to his own 
experiments more than two thirds of the interference had already 
faded, is surprising and is discussed at another place. In the pres- 
ent experiment the intervals were kept uniform at thirty seconds. 
This, it was felt, would bring out the interference more strongly. 
The results here obtained, so different from Bergstrom 's, were con- 
sequently not due to less rigorous conditions but to more rigorous. 

The results of the card-sorting experiment show that for pur- 
poses of further investigation the alternate method and the four-by- 

2 Bergstrom, loc. tit., p. 436. 



DISCUSSION AND SUMMARY 71 

four trial method of Group III. are the best. Nothing new is yielded 
by the eight arrangement method except that the interference is not 
much more, if any, with eight than with four repetitions, and that 
it is sooner overcome. The four-trial method seems to be the best 
employed by the writer. 

2. Relation of Interference to Practise Effect 

The specific problem with which Bergstrom was concerned in his 
second report on interference effect was its relation to the practise 
effect, as to whether it was greater, equal to, or less than the practise 
effect. His conclusion was that the interference effect was equal to 
the practise effect. 3 He also says that if the experiment had been 
taken at the same stage of practise as the one he previously per- 
formed the interference effect might have been greater than the 
practise effect. He thinks that the previous and opposing associa- 
tions are not effaced because they have the same effect on a third 
arrangement as they have on each other. Bair finds no such large 
amount of interference and thinks a large part of Bergstrom 's is 
due to indisposition on the part of the subject. 4 

Bergstrom had only one arrangement, that of alternating, and 
conducted it for just eight repetitions, which is included in one day 
of my experiment. He might use the same cards after several weeks 
for another similar series but was sure that at that time no practise 
effect remained over. Then in the second place he used only one sub- 
ject. With only one subject for such a short time he could hardly 
draw his strong conclusion, for several of my subjects did not show 
improvement until the second day, and had they been all used for 
just one day there would have been little improvement. 

All of the twenty-six subjects in the present experiment show 
interference effect. Immediately they show more than Bergstrom 's 
for the sortings were only 30 seconds apart. This is not a matter of 
indisposition or laziness but interference. The hardest work of the 
subjects was done right after the change and just when the interfer- 
ence showed most. Except when a record was to be broken the sub- 
jects worked hard to keep their time from increasing. Only one 
subject did not do this and he showed laxness of interest at several 
points. In spite of hardest work at such times every individual 
shows immediate interference, and those showing most improvement 
often show greatest immediate interference. 

But the interference is overcome and the two associations become 

3 Bergstrom, loc. cit., pp. 440, 441. 

4 Bair, loc. cit., p. 47. 



72 INTEEFEEENCE AND ADAPTABILITY 

automatic. The interference bears a decreasing ratio to the practise 
effect. Bergstrom assumes that, if the interference and practise 
effects are directly proportional to the number of repetitions, the one 
will be equal to the other times a certain constant. If this constant 
is equal to 1, interference is equal to the practise, if greater or less 
than 1, the interference is greater or less than the practise. If they 
are not directly proportional to the repetitions and yet hold the same 
relation to each other, then both would have the form of the true 
practise curve, or nearly so at least, as the mechanical conditions of 
the experiment admit. However, since the curves of the two opposing 
associations follow the parallel of the abscissas he holds that the inter- 
ference and practise effects do vary directly with the number of 
repetitions and hold the constant relation of one to one to each other 
and are therefore equal. 

The curves of the present experiment show that in simple prac- 
tise the practise effect varies with the number of repetitions though 
not directly proportional for the curve is concave. The question 
then arises whether the interference varies in the same way. If it 
does its relation to the practise effect would be constant. The con- 
stant quantity would be less than 1 if the curve having interference 
shows any practise effect. 

But in the present experiment the interference effect does not 
vary with the number of repetitions in the same way as does the 
practise effect. Bergstrom showed that after twenty-four hours there 
is no trace of interference left, and the present experiments indicate 
no interference from the previous day. The practise of one day 
however begins with the strength of the association of the previous 
day. Thus on the first day alone would the interference effect and 
practise effect be based upon the same number of repetitions. On 
the succeeding days the interference effect would be based only 
upon the immediately preceding opposing repetitions while the prac- 
tise effect would be based on all the repetitions of the entire experi- 
ment. There can then be no constant relation of the interference 
effect to the practise, but a variable and continually decreasing re- 
lation. 

That there is a variable and decreasing relation the curves of the 
alternate group most clearly show. The practise curve is concave, 
the alternate group almost a straight line but continually improving 
to the end. The interference is therefore continually becoming less 
as related to the practise and if the experiment were carried on for 
a very long time the two would undoubtedly come together. There 
is temporary disadvantage to be overcome, which would make just 
a little difference but would become infinitely small. The interfer- 



DISCUSSION AND SUMMAEY 73 

ence then seems to hold a variable relation to the practise, being just 
less than 1 at the beginning and approaching 0. 

The curve of Group IV. is just as concave as that of the practise 
group. The interference is readily overcome within the periods 
themselves and new practise effect is continually gained as if the 
interference were not present. It is simply temporary within each 
change of arrangements. 

In Group III. the curve shows slightly less improvement than that 
of the practise group, but it is nevertheless concave and continually 
reaches the practise group. An indefinite amount of practise would 
bring the curves closer together and the immediate interference of 
the change would show less and less. 

That the interference is an incident of the course of two associa- 
tions becoming automatic is clear, but it is overcome, and the two 
opposing associations become automatic in each of the three groups, 
with the advantage to those groups having the greater number of 
consecutive repetitions before changing to an equal number of the 
opposing reaction. 

3. Physiological Considerations 

The question has been raised as to the condition of the neural 
paths of the previous association when the new association becomes 
automatic. Miinsterberg held that physiologically there remains a 
molecular disposition of the paths used so that they are more easily 
reopened when returned to than in the first practise. 5 Bergstrom 
asks whether the old association is effaced after the practise of the 
new one. 6 He concludes that it is not because if a third arrange- 
ment A 3 is sorted it shows the interference of A x the same as A 2 does. 
He further holds that the interference effect of the A 1 A 2 series is no 
less than that of the A 1 B 1 series, which we should expect to be the 
case if the opposing associations had partially effaced each other. 

What physiological explanation would then fit his conclusion that 
the interference effect is equal to the practise effect? If an associa- 
tion fixed by a certain number of repetitions has a well-worn path- 
way of discharge, that particular association ought to function more 
readily and automatically at the nth repetition than it did at the 
first, unless it is effaced. His conclusion seems to me contrary to all 
that we know of the neural process of habit formation. That it is 
not effaced seems true but then it should function automatically. 

The results of the present experiment show just what the physio- 
logical facts would lead one to expect. The associations are not 

5 Miinsterberg, loc. cit., p. 71. 

6 Bergstrom, loc. cit., p. 440. 



74 



INTEBFEBENCE AND ADAPTABILITY 



effaced but continually become better worn and function more read- 
ily. The high rise in the curve of Group III. comes back to the prac- 
tise level almost immediately, showing that the association is as 
strong as before the interference. The same thing is true to a greater 
degree in Group IV. In the alternate group the first sorting of each 
day is distinctly better than the others, showing that the association 
has become well fixed. 

Fig. 2 is a schematic representation of the neural connections in 



1? Ml 




Fig. 2. S, S 2 , • • • represent the individual sense impressions received from 
the various cards coming in to the sense centers A, A 2 , .... In the first arrange- 
ment these are discharged into the motor cells B 1} B x 2 , ••-, so as to bring on the 
movements M 1} M x 2 , • • • throughout the first series. The sense impressions from 
the stimulus in the second arrangement are the same, so that from the same 
sense centers A, A 2 , . . . there are again discharged impulses, but these pass into 
motor cells B 2 , B 2 2 , . . . , which bring about the movements required in the second 
arrangement, represented by M 2 , M 2 2 , • • • throughout the entire series. According 
to the law of contiguity connections are worn between A 1 , A 2 , . • • , as shown by 
the dotted line. Likewise connections are worn between B 1} B 2 , • . . and between 
B 2 , B 2 2 , .... There are also connections formed between the sensations of the 
movements and the original sense center as shown by the dotted lines. We have 
established connections between the sense center and two opposing motor cells 
and consequent movements. Both, however, become automatic and when S is 
started each will follow according to the law of habit. The movements will 
follow one arrangement or the other, according which is started and receives the 
temporary advantage. 



the case of the card sorting. S represents the card stimuli pouring 
into the sense centers A. In the first arrangement there is a certain 
pathway worn S, A, B x , M lf and so on for the whole ten cards. In 
the second arrangement we have the same stimulus, and the same 



DISCUSSION AND SUMMABY 75 

sense center effected but the discharge is through a different motor 
cell and a subsequent different movement, the whole path being 8, A, 
B 2 , M 2 and so on through the entire ten cards. There is another set 
of stimuli coming from the arrangements which are different in the 
two cases and the neural connections of these determine whether A 
will discharge into B 1 or B 2 and consequently give movement M 1 or 
M 2 . But out of A there are these two pathways of discharge for the 
same stimulus and neither is effaced, but both are well worn. Now 
A, by the law of contiguity connects with A 2 , A 3 , . . ., B x connects 
with B x z , B x 3 , . . ., while B 2 connects likewise with B 2 2 , B 2 3 and 
each of the movements M 1 and M 2 connect with A. So all the con- 
nections are formed as in forming a single habit, except that here 
we have two opposing habits and yet both of them becoming auto- 
matic. As to which direction the discharge will go depends on the 
larger complex in which this situation lies, but the fact is that both 
of them are open and ready to discharge. Miinsterberg said that the 
discharge will follow either path and that it will not divide. This 
is the case in the experiments, and this the figure in a schematic 
manner attempts to show in the neural connections. 

4. Adaptability 

In the introduction it was stated that adaptation is the general 
character of mental development, that adaptative reconstruction is 
the general form of change which is incessantly renewed so long as the 
individual continues to live, and that this embodies an elaborated 
form of response and a modification of the response to meet a change 
in the system of stimuli. The question of adaptability was found to 
have wide practical interests, racial, political, religious, social and 
industrial. To investigate these in their broad relations is impossible 
under experimental conditions. Observation shows that in all these 
fields adjustments are made with greater or less ease among individ- 
uals and groups. The friction which opposes these adjustments or 
in a more general sense adaptation, is interference. Interference 
seems to be present to a greater or less extent among all such ad- 
justments. 

For the making of these adjustments the nervous system has 
groups of inherited tendencies, the simple elements of which are as- 
sociative connections. With these associative connections the ex- 
periment has had to do. If these larger complexes have adjustment 
properties we should expect the associative elements to have them 
also, though not to such a great extent. If an individual can adapt 
himself in these wider fields of interest and activity he should be 



76 INTEBFEBENCE AND ADAPTABILITY 

able to do the same to a lesser degree in the simple associations. 
What is true of life should be found true in the laboratory. 

The experiments show that on simple association interference is 
an incident, but only an incident and not fundamental. Adaptation 
is the fundamental thing, because the two associations do become 
automatic. In the wider interests interference is an incident but 
adaptation is fundamental. This is true in religious conversion, in 
industrial changes, in social readjustments, in racial migrations and 
in every form of life where variations occur in the environment. 
That it is true in associaton per se preserves a unity in the nervous 
organism. 

Bergstrom says in speaking of these wider applications of the 
problem: 7 "The nervous system has, as is well known, inherited 
tendencies of growth and adjustment to external circumstances. 
Perhaps the simplest of these for the organization of nervous activ- 
ity is the tendency of nerve currents to run from one pattern to the 
next succeeding. This is modified in many ways by special tenden- 
cies of a higher order, which may be classed as fundamental 
practical adjustments or practical interests. If these are given 
opportunity to influence the results, we are not dealing with 
associations per se, but with these as modified by other more pow- 
erful forces. . . . There are besides great numbers of secondary 
tendencies by which simple successive association is transformed. 
Moreover where the conditions are more complex than in this ex- 
periment certain conditions may enter and change the results. A 
person who speaks several languages finds that the words of the 
same language tend to be recalled together. Some persons also 
know and can use two different systems of shorthand. In these 
cases the elements associated are used as members of a group, for 
the exclusive employment of which there seems to be a strong 
tendency. The inconvenience of interference is thus to some extent 
avoided in these cases, but probably only by a proportionate ex- 
penditure of energy." 

In other words the elements of the complexes show an eternal 
interference to the tendencies of the complexes themselves. It is 
rather peculiar that an individual can use automatically two sys- 
tems of shorthand, each simple association of which excludes the 
opposing one, and yet can never learn to shuffle a few cards when 
their associations exclude each other as Bergstrom 's discussion indi- 
cates. That there are these higher complexes and that they show 
wider adaptive tendencies is freely admitted, on the principle that 
the higher the process the wider the differences and the greater the 

7 Bergstrom, loc. cit., p. 442. 



DISCUSSION AND SUMMABY 77 

plasticity. But that there is an irreconcilable conflict is denied. 
That the larger adjustments are made only because the superior 
energy overcomes the inferior associative element does not give us a 
unity but gives us an unexplained difference. If this were the case 
then no investigations of association would have the slightest value 
in practical interest and the results of experimental psychology 
would be in endless contradiction with the truths obtained by obser- 
vation and general experience. Though we are not yet able to show 
the correlation between results on simple association and these higher 
adjustments the search is not futile, but it would be hopeless if the 
results on association per se conflicted irreconcilably with these 
tendencies which are only groups of association elements, and their 
adjustment had to be explained on the ground that the lower ele- 
ments are overcome by their greater energy. 

The individual differences in adaptability are great and this is 
what general experience confirms. The discussion of plasticity as a 
section in "Individual Differences" shows a correlation between the 
initial efficiency and the improvement under conditions of inter- 
ference. This correlation is higher in the groups having interference 
than in the practise group. The more complex the situation is and 
the more it calls for adaptability and adjustment in the face of inter- 
ference, the more does the individual ability appear. Greater abil- 
ity of performance at the start indicates greater power of adaptabil- 
ity. The fittest will adapt best and survive, the ones most 
accustomed to the one situation will most readily adapt themselves 
to the new. The more fully one set of habits is built up the better 
fitted is the organism for having many habits with mutually ex- 
clusive associations. 

According to Bryan and Harter the higher the organism the 
more complex the hierarchy of habits. 8 The higher the organism the 
greater the power of adaptability. The experiments show that there 
is progress in spite of interference because fully developed habits 
are formed, and the more completely each of these habits are formed 
the less influence interference has and the greater the adaptability 
of the individual. Adaptability is not manifest because there is 
little interference from a weakly opposing association, but because 
all the associations are strong, and the interference has no power of 
effacing the opposing associations. While Bryan and Harter dis- 
cuss a different problem in their hierarchy of habits, yet the same 
general conditions of adaptability seem to underlie the ready forma- 
tion of a hierarchy of habits, and the formation of a complex of 

8 Bryan and Harter, ' ' On Learning the Telegraphic Language, ' ' Psych. 
Bev., 6, 1899. 



78 INTERFERENCE AND ADAPTABILITY 

habits as in the present experiment. Their contention also that the 
hierarchy of habits is an index of higher type of organism agrees 
with the building in of habits of the present experiment. 

The discussion of "variability"- also brings out the fact that in- 
dividual differences are greater under conditions of interference than 
in the simple practise groups. The average deviation is greater in 
Group III. than in the practise group. The variation in the rates of 
improvement as expressed by the Pearson formula are greater after 
the "break" than before in all the groups of the typewriter experi- 
ment, and also among the groups of the card-sorting experiment the 
variability of the groups under interference is greater than that of 
the practise groups. The sex differences are not so pronounced. 

Ethical Implications 

Professor James has pointed out the enormous consequences of 
habit as being the precious conservative agent of society. 9 The 
plaster of life is early set and forever thereafter we are content to 
remain in the mold. Men grown old in prison ask to be readmitted. 
While this is true there is another side to the truth. Some in whom 
the mold has long been set move from the foreign land to this and 
enjoy the remainder of their days. There are limits to which the 
plaster will reset to the new conditions. There are adjustments made 
long after the old associations had been firmly fixed. After the 
change the new forms for itself another mold of habit and if the 
former is not returned to will be just as well set as if it were the 
only one. If the former is returned to the individual will be as per- 
fectly adapted to either as he once was to the first. 

One of Professor James's oft-quoted maxims is "Never suffer an 
exception to occur until the new habit is securely rooted in your 
life." How true this is many of the subjects in the typewriting ex- 
periment can fully testify. Often when the new order seemed to be 
well established and the old troubled them little, one relapse would 
set them wrong for the rest of the experiment and it would be harder 
for them to overcome it than after the immediate ' ' break. ' ' 

There is another truth which seems to the writer to have great 
importance and value. Do not passively resist the temptation of the 
old stimulus, but respond to it by another action which will exclude 
the previous action. Let the reformed drunkard resist the tempta- 
tion to drink by every time taking some little refreshment which will 
give a definite response to the stimulation, but which will exclude 
the former. Religious societies have long recognized in a general 
way that the new convert must have other work to do to satisfy his 

9 William James, " Principles of Psychology," Vol. 1, p. 121. 



DISCUSSION AND SUMMARY 79 

impulses. Only by action which will exclude the former association 
will there be real success in excluding the former and a true method, 
psychologically speaking, of ingraining the latter. 

Summary 

The results of the experiments may be summed up as follows : 

1. When two opposing associations, each of which excludes the 
other, are alternately practised with one, four, or eight repetitions of 
each association before the other is resumed, the opposing associa- 
tions have an interference effect upon each other in all the subjects. 
The interference effect grows less and less while the practise effect 
becomes greater. The interference effect is gradually overcome and 
both opposing associations become automatic so that either of them 
can be called up independently without the appearance of the other. 
The curves of the alternating group follow a straight but descending 
line and gradually approach the true practise curve. The curves in 
which four or eight repetitions of the one association are given before 
the other is resumed are concave and closely approach the practise 
curve. The individual differences in the rate of improvement are 
as great as in the absolute time records, but in no case is the interfer- 
ence effect equal to the practise effect. Adaptability is fundamental 
with individual differences; interference is an incident in the course 
of automatization of the two opposing associations. 

2. When a change in reaction to several of a series of long prac- 
tised stimuli is introduced, as in the typewriting experiment, there 
is great immediate interference effect. This is shown by the increase 
in time and the recurrences of the former associations. The improve- 
ment is rapid, the interference effect is overcome, and the previous 
level of efficiency attained. Individual differences are greater than 
before the change was introduced. The number of recurrences of 
the former association varies from 2 to 66. There are no sex differ- 
ences, except that the women are more variable than the men. 

3. There is a positive correlation between the adaptability of the 
eight subjects of the preliminary group of the typewriting experi- 
ment and the traits of individuality, independence and originality. 

4. There is a positive correlation between adaptability as shown 
by the discrimination to red after long practised association with 
blue, and the color naming test of 100 colors. 

5. An error committed in practise tends to introduce interfering 
associations which will cause other errors. In some cases this inter- 
ference has a general effect which causes various errors; in other 
cases it has a specific effect which causes a repetition of the error in 



80 INTERFERENCE AND ADAPTABILITY 

succeeding trials. Some individuals are affected mostly in the first 
way, while others are affected chiefly in the second way. There are 
great individual differences in the interference caused by errors. 

6. There is a high correlation between initial and final efficiency 
which shows that the more efficient improve as much as or more than 
the less efficient. This correlation is higher when interference is 
present than it is in simple practise, thus bringing out the individual 
ability more clearly. There is also a slight correlation between initial 
efficiency and rate of improvement in the groups having interfering 
associations, while there is none in either the simple practise group 
or the typewriting experiment. 

7. There are no significant sex differences in rate of improvement. 
The men show greater immediate effect after the change from one 
sorting to another, but they very rapidly get back to their former 
level. 

8. The variability is greater when interference is present than 
when it is not. This is shown in a comparison of the practise group 
with the others in the card-sorting experiment and also by compar- 
ing the rate of gain after the break with that before the break in the 
typewriting experiment. The women show greater variability in re- 
lapses but not in actual time records nor in rates of gain. 



VITA 

Born at Hartville, Ohio, March 14, 1883. Received preparatory 
training at Louisville High School and Mt. Union College. Taught 
one year in Ohio public schools. B.A., Juniata College (Penn.), 
1908; studied at Crozer Seminary and University of Pennsylvania, 
1908-9; at Columbia University and Union Theological Seminary, 
1909-12 ; at the University of Leipzig, summer of 1910 ; B.D., Union 
Theological Seminary, 1911. 



81 



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Deacidified using the Bookkeeper process. 
Neutralizing agent: Magnesium Oxide 
Treatment Date: Nov. 2004 

PreservationTechnologies 

A WORLD LEADER IN PAPER PRESERVATION 

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